Polypeptides targeting glycosylated MUC2 proteins, methods of synthesis, their nucleic acids and uses thereof

ABSTRACT

The invention relates to polypeptides, defined through a consensus sequence, having a length from 10 to 80 amino-acid residues, and whose polypeptidic sequence comprises or consists of the consensus sequence P1(X a )P3(X b )P5(X c )P6(X d )P7 (SEQ ID NO: 1), presenting specific patterns. The polypeptides of the invention target glycosylated Muc2 proteins. The invention also relates to methods of synthesis of such polypeptides, to their nucleic acids and uses thereof. The polypeptidic sequence of the polypeptides of the invention can be part of the N-terminal sequence of a mucus-binding (MUB) domain, especially a mucus-binding (MUB) domain of several species. The invention also relates to chimeric molecule(s) comprising such polypeptides, which are labelled, and vectors, especially plasmids and population of cells or composition comprising polypeptides of the invention. Synthesis methods encompass biotechnological or chemical production. Polypeptides of the invention can be used in staining experiments, as a probe or marker for staining Muc2 protein(s) contained in mucus layer(s), to detect in vitro mucus production or mucus composition in human colon or monitoring any one of the following disease conditions: neoplasic disease(s), including mucinous carcinoma(s), gastric cancer(s) or colorectal cancer(s), especially colon cancer(s), cystic fibrosis, intestine inflammatory disease(s) such as inflammatory bowel disease (IBD) and ulcerative colitis. The invention also relates to a method for manufacturing a medicament. In a particular embodiment, use of polypeptides of the invention can be made for marking neutrophiles.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jun. 9, 2014, is named 106877-0111_SL.txt and is 148,084 bytes in size.

The invention relates to isolated polypeptide(s) interacting with glycosylated Muc2 proteins in mucus layers of various biological tissues, especially colonic tissue. The invention also relates to a method for synthesizing such polypeptide(s) via chemical synthesis (i.e. involving solid phase synthesis) or via biotechnological production.

Therefore, the invention also relates to nucleic acid molecule(s) encoding polypeptide(s) of the invention, as well as nucleic acid delivery systems such as vectors and cells or populations of cells comprising nucleic acid molecule(s) or vector(s) in relation with the invention.

The invention also relates to composition(s) comprising the same, in particular to pharmaceutical composition(s) including if necessary carrier(s) or adjuvant(s).

The invention may be used for staining cell(s) in in vivo, ex vivo, especially in vitro, experiments, in particular in live microscopy experiments.

According to a particular embodiment, the molecule(s) comprising a polypeptide of the invention are used as probe(s) for staining mucus potentially containing Muc2 protein(s), especially, but not exclusively, colonic mucus produced by eukaryotic cell(s).

Mucus production or composition in animal or human body might be modified as a result of physiological events as well as a result of several disease conditions such as neoplasic disease(s), non-limitatively including mucinous carcinoma(s), gastric cancer(s) or colorectal cancer(s), especially colon cancer(s), or diseases such as cystic fibrosis or intestine inflammatory disease(s) such as inflammatory bowel disease (IBD) and ulcerative colitis.

In addition to the possibility to use the claimed molecule(s) for immunostaining fixed cells, and according to another particular embodiment, the molecule(s) of the invention can also be used as a marker of degranulation event(s), especially in living neutrophiles.

The human gastro-intestinal mucus layer establishes a physical barrier between the luminal content and the epithelial surface. This layer provides efficient protection against luminal aggressions [1] and is continuously removed (enzymatic destruction and mechanical shearing, i.e. peristaltism) and renewed through the secretory activity of epithelial goblet cells [2]. It was recently suggested that the mucus layer allows constitution of an oxygen gradient diffusing from the intestinal epithelium into the lumen [3] even though no quantification was yet achieved. This gradient plays a critical role in Shigella virulence modulation in the vicinity of the intestinal epithelial barrier, and possibly controls the virulence of other pathogens in addition to keeping strictly anaerobic bacteria away from the vicinity of the epithelium [4]. In vivo observations are a prerequisite for oxygen detection in this environment. In order to study this largely unexplored microenvironment at epithelial interface using emerging live imaging techniques (two-photons microscopy, fluorescent life-time imaging (FLIM) and high resolution microscopy (PALM and STORM)), it is required to develop specific, non-toxic and non-destructive colonic mucus fluorescent marker(s).

The colonic mucus is composed of two distinct layers; a firmly adherent layer associated to the epithelial surface and a loosely, more fluid, adherent one. The later is probably the result of bacterial degradation and proteolysis [5]. It is composed of 95% water and 5% mucin glycoprotein molecules, salt, immunoglobulins (IgA and IgG) and trefoil peptides [6]. Among secreted mucins, the main gel forming molecules are Muc2, Muc5ac, Muc5b and Muc6 (expressed from chromosome 11p15.5) [7], Muc2 is the predominant mucin in the colonic mucus layer and is highly glycosylated, allowing its protection from proteolysis in the lumen[8] [9] [10] [11]. Muc2 shows differential glycosylation profiles in the small intestine (ileum) and in the large intestine (colon) respectively enriched in sialylated and sulfated oligosaccharide species [9] [12]. Mucus production and composition modulations are commonly observed in the major inflammatory bowel diseases (IBD) like Crohn disease [13] [14] and ulcerative colitis [15]. Specifically, Muc2 expression is upregulated in malignant tumors of a broad range of organs [16] including lung [17], stomach [18] [19], breast [20], prostate [21], bile ducts [22] and colon [23]. Detecting the nature and amount of mucus is important to envision the diagnostic and prognosis of various pathological conditions.

Part of the process of identifying a molecule able to specifically bind human colonic mucus, the mucus adhesion properties of commensal bacteria were observed. These microorganisms, such as Lactobacillus spp, express cell-surface proteins named Mucus binding proteins (MucBP, PFAM PF06458) that are involved in intestinal mucus adhesion. As an example, in the human intestine, Lactobacillus reuteri (L. reuteri) has been identified as an inhabitant of the ileum and colon loosely adherent to the mucus layer [24]. The MucBP protein family is characterized by the presence of well-conserved mucin binding domains (MucBD) expressed as repeats in many cell-surface MucBP of L. reuteri [25] [26]. Considering that there is a need for tools suitable for mucus observation in various pathological situations, in particular for mucus observation in specific intestine compartments affected by such pathological situations, the inventors have identified in several bacteria, regions whose amino-acid sequences may be used to prepare polypeptides useful for mucus observation.

Through this study, novel binding properties of L. reuteri Mucus Binding Proteins to human colonic mucus were characterized. It was demonstrated that the considered domain of interest binds to mucus proteins independently of the previous characterized MUB domain. This domain is a novel MucBD of 70 amino acids length, hereafter named MUB₇₀, which can be individualized as a polypeptide able to oligomerize and to specifically bind the glycosylated moiety of Muc2.

Therefore, the invention relates to a polypeptide having a length from 10 or from 17 to 80 amino-acid residues and whose polypeptidic sequence comprises or consists of the consensus sequence P1(X_(a))P3(X_(b))P5(X_(c))P6(X_(d))P7 (SEQ ID NO: 1) disclosing, from N-terminal to C-terminal ends, patterns P1, P3, P5, P6 and P7, which are defined as follows:

-   -   P1 represents the amino-acid sequence VXYXD/N, where X         represents any amino-acid,     -   P3 represents the amino-acid sequence GY,     -   P5 represents the amino-acid sequence F/YD,     -   P6 represents amino-acid residue D, and     -   P7 represents amino-acid residue Q;         and wherein said patterns are further characterized by spacer         amino-acid segments (X_(a)), (X_(b)), (X_(e)) and (X_(d))         containing respectively a, b, c and d numbers of any amino-acid         residue(s) which are defined as follows:     -   a ranges from 2 to 33,     -   b ranges from 2 to 11,     -   c ranges from 1 to 2,     -   d ranges from 1 to 3;         and wherein said polypeptide interacts with glycosylated Muc2         protein(s), in particular interacts with sulfated moieties of         glycosylated Muc2 protein, of human colonic mucus or human         intestinal mucus.

The consensus sequence of SEQ ID NO: 1 can also be written: VXYXD/N(X_(a)) GY(X_(b)) F/YD(X_(c))D(X_(d))Q, with spacer amino-acid segments (X_(a)), (X_(b)), (X_(e)) and (X_(d)) as defined above.

According to a particular preferred embodiment, the polypeptidic sequence of a polypeptide of the invention comprises or consists of the consensus sequence P1(X_(m))P2(X_(n))P3XP4(X_(p))P5(X_(q))P6(X_(r))P7X₃P8 (SEQ ID NO: 2), X being any amino-acid residue, said consensus sequence disclosing, from N-terminal to C-terminal ends, patterns P1, P2, P3, P4, P5, P6, P7 and P8, which are defined as follows:

-   -   P1 represents the amino-acid sequence VXYXD/N, where X         represents any amino-acid,     -   P2 represents the amino-acid sequence YS/TT,     -   P3 represents the amino-acid sequence GY,     -   P4 represents amino-acid residue L,     -   P5 represents the amino-acid sequence F/YD,     -   P6 represents amino-acid residue D,     -   P7 represents amino-acid residue Q, and     -   P8 represents amino-acid residue V,         and wherein said patterns are further characterized by spacer         amino-acid segments (X_(m)), (X_(e)), (X_(p)), (X_(q)) and         (X_(r)) containing respectively m, n, p, q and r numbers of any         amino-acid residue(s) which are defined as follows:     -   m ranges from 1 to 23,     -   n and p range from 1 to 10,     -   q is 1 or 2,     -   r ranges from 1 to 3.

Consequently, the consensus sequence identified under consensus sequence (SEQ ID NO: 2) can also be written VXYXD/N(X_(m))YS/TT(X_(n))GYXL(X_(p))F/YD(X_(q))D(X_(r))QX₃V, wherein X is a symbol representing any amino-acid, including modified or non-conventional amino-acids, said symbol X being, when necessary, followed by a subscript number indicating the number of amino-acid residues incorporated into the consensus sequence. The absence of subscript number indicates that only one amino-acid residue is incorporated. The same abbreviations are generally used for the purpose of the present disclosure, unless differently specified.

In the consensus sequences disclosed above and more generally in the amino-acid sequences disclosed herein, the symbol “/” inserted between two amino-acid residues means that any of these two amino-acid residues is to be found in a polypeptide of the invention encompassed by consensus sequences disclosed herein, as an alternative. As a consequence, a symbol such as “X/X” represents the presence of only one amino-acid residue having one or the other proposed nature. A symbol such as “D/N” represents only one amino-acid residue chosen among amino-acid D and amino-acid N. Conventional abbreviations are used herein, with respect to the single letter amino-acids alphabet. Parenthesis symbols “( )” are used to separate several positions within a consensus sequence, when alternatives are possible for two consecutive positions within said consensus sequence.

By a “pattern”, it is meant an amino-acid residue or a series of amino-acid residues that are to be found substantially unchanged, in their nature and/or sequence(s) and/or position(s), within all polypeptides encompassed by the consensus sequences disclosed above. The described patterns are thus further characterized, as a whole, by the spacer segments “Xi” providing a determined distance (expressed as a number of amino-acids) between especially two of them. The consensus sequences disclosed herein were identified starting from sequence alignments performed by the inventors, as exemplified within the present disclosure, through conventional alignment methods or algorithms.

According to a particular embodiment, a polypeptide of the invention has a length from 17 to 80 amino-acid residues and is selected from:

-   -   i. A polypeptide whose polypeptidic sequence comprises or         consists of SEQ ID NO: 3, or;     -   ii. A polypeptide whose polypeptidic sequence comprises or         consists in a sequence having at least 23% or at least 30%         identity with SEQ ID NO: 3, or;     -   iii. A polypeptide whose polypeptidic sequence comprises or         consists of a fragment, especially a fragment of contiguous         amino-acid residues of at least 10 or 17 amino-acid residues, of         any one of the sequences defined in i) or ii);         said polypeptide interacting with glycosylated Muc2 protein(s),         in particular with sulfated moieties of glycosylated Muc2         protein, of human colonic mucus or human intestinal mucus.

According to specific embodiments of the invention, a polypeptide of the invention has a polypeptidic sequence comprising or consisting of a fragment of the sequence of any one of SEQ ID NO: 5 to SEQ ID NO: 16, or any one of SEQ ID NO: 19 to SEQ ID NO: 22, especially a fragment within the N-terminal extremity of said polypeptide, or has an amino-acid sequence comprising or consisting of any one of SEQ ID NO: 23 to 61 or a variant or a fragment thereof.

In a particular embodiment, the polypeptide of the invention has a length from 38 to 43 amino-acid residues and its polypeptidic sequence also comprises the consensus sequence GY(X_(s))F/YD(X_(t))Q (SEQ ID NO: 67) where X represents any amino-acid, said consensus sequence disclosing, from N-terminal to C-terminal ends, spacer amino-acid segments (X_(s)) and (X_(t)) containing respectively s and t numbers of any amino-acid residue(s) which are defined as follows:

-   -   s ranges from 12 to 16, in particular is 12, 13, 14 or 15,     -   t ranges from 5 to 9, in particular is 7 or 6 or 8.

As illustrated in FIG. 32, SEQ ID NO: 67 can differently be written as consensus sequence P8(X_(s))P9(X_(t))P10, X being any amino-acid residue, said consensus sequence encompassing, from N-terminal to C-terminal ends, patterns P8, P9, P10, which are defined as follows:

-   -   P8 represents the amino-acid motif GY,     -   P9 represents the amino-acid motif F/YD,     -   P10 represents the amino-acid residue Q,         and wherein said patterns are further characterized by spacer         amino-acid segments (X_(s)) and (X_(t)) containing respectively         s and t numbers of any amino-acid residue(s) which are defined         as follows:     -   s ranges from 12 to 16, in particular is 12, 13, 14 or 15,     -   t ranges from 5 to 9, in particular is 7 or 6 or 8.

In a more particular embodiment, P8 and P9 respectively correspond to P3 and P5 of SEQ ID NOS 1 or 2.

In a more specific embodiment, the polypeptide of the invention has a length from 38 to 43 amino-acid residues and its polypeptidic sequence also comprises the consensus sequence GYXL(X_(u))F/YDXD(X_(v))QX(Y/F/W)(T/Y/E)V (SEQ ID NO: 68) where X represents any amino-acid, said consensus sequence disclosing, from N-terminal to C-terminal ends, spacer amino-acid segments (X_(u)) and (X_(v)) containing respectively u and v numbers of any amino-acid residue(s) which are defined as follows:

-   -   u ranges from 10 to 14, in particular is 10, 11, 12 or 13 or 14,     -   v ranges from 2 to 6, in particular is 4 or 2, 3, 5.

As illustrated in FIG. 32, SEQ ID NO: 68 can differently be written as consensus sequence P8′(X_(u))P9′(X_(v))P10′, X being any amino-acid residue, said consensus sequence encompassing, from N-terminal to C-terminal ends, patterns P8′, P9′, P10′ encompassing patterns P8, P9 and P10 defined herein, said patterns P8′, P9′, P10′ being defined as follows:

-   -   P8′ represents the amino-acid sequence GYXL, X being any         amino-acid residue,     -   P9′ represents the amino-acid sequence F/YDXD, X being any         amino-acid residue,     -   P10′ represents the amino-acid sequence QX(Y/F/W)(T/Y/E)V, X         being any amino-acid residue,         and wherein said patterns are further characterized by spacer         amino-acid segments (X_(u)) and (X_(v)) containing respectively         s and t numbers of any amino-acid residue(s) which are defined         as follows:     -   u ranges from 10 to 14, in particular is 10, 11, 12 or 13 or 14     -   v ranges from 2 to 6, in particular is 4 or 2, 3, 5.

By “variant”, it is meant a polypeptide resulting from limited variations in the sequence of the polypeptide of reference, variant polypeptides encompassing polypeptides having at least 23%, 25%, 29%, 40% or 50% identity with the sequence of reference. According to a particular embodiment, identity percentages reach 60%, 70%, 80% or more. In a particular embodiment, identity percentages are at least of 85% or at least of 90%.

According to another particular preferred embodiment, the polypeptidic sequence of a polypeptide of the invention comprises or consists in a sequence having at least 30% identity with SEQ ID NO: 3 (also referred to as MUB₇₀ herein), or comprises or consists in SEQ ID NO: 3, or comprises or consists of a fragment, especially a fragment of contiguous amino-acid residues of at least 10 amino-acid residues, in particular at least 17 amino-acid residues, of any one of the sequences or fragment thereof encompassed by the consensus sequences SEQ ID NO: 1 or SEQ ID NO: 2 or fragments thereof, or of any one of the sequences or fragment thereof encompassed by the sequences having at least 30% identity with SEQ ID NO: 3 or fragment thereof.

According to a particular embodiment, a polypeptide of the invention comprises or consists in a sequence having at least 23%, 25%, 29%, 40% or 50% identity with SEQ ID NO: 3 or SEQ ID NO: 58, or a fragment thereof. Identity percentages can reach 60%, 70%, 80% or more. In a particular embodiment, identity percentages are at least of 85% or at least of 90%. Such a polypeptide can be the polypeptide of SEQ ID NO: 67 or the polypeptide of SEQ ID NO: 68.

According to a particular embodiment, a polypeptide of the invention consists of a fragment of contiguous amino-acid residues of about 20, 30 or 40 and up to 50 amino-acid residues of SEQ ID NO: 3, in particular consists of a fragment encompassing the sequence of any one of SEQ ID NOS 58, 59, 60 or 61, or having the sequence of any one of SEQ ID NOS 58, 59, 60 or 61.

According to a particular embodiment, a polypeptide of the invention comprises or consists in a sequence having at least 23%, 25%, 29%, 40%, 50%, 70% or at least 90% identity with any one of SEQ ID NOS 58, 59, 60 or 61, or a fragment thereof. In a particular embodiment, identity percentages are at least of 80 or 85% or at least of 90 or 95%.

According to a particular embodiment, a polypeptide of the invention comprises or consists of any one of SEQ ID NOS 69 to 83, as disclosed in FIG. 32.

With respect to the interaction with glycosylated Muc2 protein(s) of human colonic or intestinal mucus, the expression “interacts” used herein means that a polypeptide of the invention binds said components of the mucus, or enters into close vicinity with such components when present in colonic mucus layers, i.e. loose mucus layer or firm mucus layer, or in intestine mucus.

According to a particular embodiment, a polypeptide of the invention interacts with glycosylated Muc2 protein(s) through sulfated moieties of glycosylated Muc2 protein(s).

According to a specific embodiment, a polypeptide of the invention interacts with glycosylated human, rabbit and guinea pig Muc2 protein(s) but not with murine glycosylated Muc2 protein(s).

According to a particular embodiment, a polypeptide of the invention specifically interacts with mammalian glycosylated Muc2 protein(s), and in particular with glycosylated Muc2 protein(s), from colonic mucus or intestine mucus.

The expression “specifically interacts with Muc2 protein(s)” relates to the fact that the molecule(s) of the invention do(es) not interact or not significantly interact with other secreted gel-forming mucins, taken alone or according to any combination between them, said other secreted gel-forming mucins including for example Muc5ac, Muc5b or Muc6.

According to a particular embodiment, polypeptide(s) of the invention can have a dimeric or a trimeric quaternary structure.

According to a particular preferred embodiment, polypeptide(s) of the invention are able to dimerize or trimerize.

According to a particular embodiment, a polypeptide of the invention has a length from 10, in particular 17, to 100 amino-acid residues, especially from 10 to 80 or 90 amino-acid residues, in particular up to 68, 69, 70, 71 or 72 amino-acid residues. In a particular embodiment a polypeptide of the invention has a length of 15, 17, 20, 30, 40, 50, 60, 65, 68, 69, 70, 71 or 72 amino-acid residues.

According to a particular embodiment, a polypeptide of the invention has a length of 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45 amino-acid residues.

In a particular embodiment, a polypeptide of the invention consists or contains or encompasses a sequence found within the N-terminal extremity or the C-terminal extremity of sequence SEQ ID NO: 3, or have at least 23%, 25%, 29%, 40% or 50% identity with a fragment of SEQ ID NO: 3 as found within the N-terminal extremity of said sequence or with SEQ ID NO: 58 or a fragment thereof. Identity percentages can reach 60%, 70%, 80% or more than 85% or 90%. By “N-terminal extremity of sequence SEQ ID NO: 3” it is meant the portion of SEQ ID NO: 3 that is closer to the N-terminal extremity than to the C-terminal extremity. Conversely, by “C-terminal extremity of sequence SEQ ID NO: 3” it is meant the portion of SEQ ID NO: 3 that is closer to the C-terminal extremity than to the N-terminal extremity.

The length of the polypeptide may vary depending on the species, from which it was identified, especially when identified from Lactobacillus protein(s).

According to a particular embodiment, the polypeptidic sequence of a polypeptide of the invention is part of the N-terminal sequence of a mucus-binding (MUB) domain, especially a mucus-binding (MUB) domain of a species selected amongst the Lactobacillus, Streptococcus, Cryptobacterium, Weissella, Granulicatella or Leuconostoc species, and in particular is part of any one of the repeats of a L. reuteri mucus-binding (MUB) domain (For example it is part of a polypeptide having a sequence disclosed in Table 2).

By “part of”, it is meant that the information relative to the contents in amino-acid residues of the polypeptide(s) of the invention (i.e. the “nature” of said amino-acid residues and their sequence arrangement) can be derived or identified or deduced from the contents of polypeptidic domain(s) or protein(s) or fragment(s) thereof identified as relevant within the present disclosure.

Polypeptides of short length may be preferred and may be obtained by shortening the amino-acid sequence of the identified polypeptides, to the extent that the shorter polypeptides keep the capacity of the original polypeptides to bind human colonic mucus through glycosylated Muc2 protein. Advantageously, a short polypeptide of the invention might be 10, or 17, or 25 to 40 amino-acid long, or 10, or 17, or 25 to 60 amino-acid long.

Examples of short polypeptide(s) of the invention include the polypeptide(s) disclosed herein under SEQ ID NOS 58, 59, 60 or 61, having a length of 40 amino-acid residues. The invention encompasses polypeptides resulting from small variations in the sequence of such polypeptides, including polypeptides having at least 23%, 25%, 29%, 40% or 50% identity with any one of SEQ ID NOS 58, 59, 60 or 61. According to a particular embodiment, identity percentages reach 60%, 70%, 80% or more. In a particular embodiment, identity percentages with respect to any one of SEQ ID NOS 58, 59, 60 or 61 are at least of 85% or at least of 90%.

The invention also encompasses polypeptides resulting from small variations in the size of such polypeptides, including polypeptides having a length of 20, 30, 35, 37, 38, 40, 42, 44, 45 or 50 amino-acid residues.

Accordingly, in a particular embodiment, polypeptides of the invention have from 38 to 43 amino-acid residues and comprise or consist of any one of SEQ ID NOS 69 to 83, as disclosed in FIG. 32, or a fragment thereof.

According to a specific embodiment, the polypeptidic sequence of a polypeptide of the invention can be found within the N-terminal sequence of the repeats of a L. reuteri mucus-binding (MUB) domain, i.e., its sequence can be identified or deduced from the N-terminal sequence(s) of the repeats of a L. reuteri mucus-binding (MUB) domain, after aligning said N-terminal sequence(s) with the consensus sequences described herein (see Table 1).

TABLE 1 MUB₇₀ repeat sequences comparison in L. reuteri mucus binding precursor AF120104. Data were obtained using BlastP software, comparing 13 MucBDs (SEQ ID NO: 5 to SEQ ID NO: 16), identified by their amino acids numbers boundaries, within AF120104 protein. MUB domain aa repeat numbers E value % identity % positive 1 548-727 2e−13 35 50 2 742-924 1e−13 35 50 3  939-1112 1e−13 32 51 4 1127-1297 1e−13 35 50 5 1317-1500 2e−86 85 91 6 1501-1684 3e−101 98 99 7 1685-1868 4e−104 100 100 8 1869-2052 3e−101 98 99 9 2053-2236 4e−104 100 100 10 2237-2420 3e−101 98 99 11 2421-2604 2e−100 98 98 12 2605-2788 3e−93 92 95 13 2974-3165 1e−08 29 47

The “repeats” of L. reuteri mucus-binding (MUB) domain are illustrated in Table 1 and the figures and the examples, as a domain encompassing around 200 amino-acid residues. Although different for each repeat, the amino-acid sequences of these repeats show common functional features related to mucus binding. The consensus sequences described herein share patterns that are considered important for said common binding functional features.

The annotated GenBank entry of the mub gene from L. reuteri, encoding the Mub protein from L. reuteri containing such a mucus-binding (MUB) domain can be found under accession number AF120104.1 (SEQ ID NOS 17 and 18).

By comparison of the Mucus Binding proteins of other organisms, especially Lactobacillus, it has been possible to determine similarly functional domains with respect to Muc2 protein binding in colonic mucus, thereby providing the definition of further polypeptides. Accordingly, the invention relates to a polypeptide having a length from 10, in particular at least 17, to 80 amino acid residues and whose sequence can be identified in the N-terminal sequence of the repeats of a Mucus Binding Domain (MUcBD) present in mucus binding protein (MucBP) of L. gasseri, L. johnsonii, L fermentum or L. Acidophilus (see FIG. 1C and Table 2), or of Streptococcus, Weissella, or Leuconostoc species (see Table 2).

According to a specific embodiment, a polypeptide of the invention comprises or consists of a fragment of the polypeptide having the sequence of any one of SEQ ID NO: 5 to SEQ ID NO: 16, or any one of SEQ ID NO: 19 to SEQ ID NO: 22, especially a fragment within the N-terminal extremity of said polypeptide, or this polypeptide has an amino-acid sequence comprising or consisting of any one of SEQ ID NOS 23 to 57 or a fragment thereof.

TABLE 2 MUB₇₀ (SEQ ID NO: 3) sequence comparison in several species.  Compared sequences are identified with their Genbank access numbers (SEQ ID NO: 23  to SEQ ID NO: 57), alignments identity results with SEQ ID NO: 3 are provided. MUB70 (SEQ ID NO: 3) VHVQYIDGETDQMLRQDDLDGYTDETIPYSTAEGIKKFEGDGYELFKDNFPAGEKFDNDDTNDQFYTVIF SEQ ID % NO: GENE ID Sbjct Identity Sequence 23. 3252355 LBA1020 | 49% VNYVDADEDNKLITSSGDLTGKAGETINYSTADTIKD mucus binding protein (34/70) LENKGYVLVNDGFPAGAKYDSDDNTTQIYTVVL [Lactobacillus acidophilus NCFM] 24. ref|ZP_04061590.1| Sbjct  44% ITYVDQTTGQTLANDQVGGKSGEAINYSTADKIKYY MucBP domain protein 57 (31/70) EDRGYVLVSDEFPTGAHFDNDASVDQTWTVTL [Streptococcus salivarius SK126] Length = 245 25. ref|NP_964063.1| Sbjct 46% VNYIDADDNNAIITSSDNLTGKAGEKIDYSTASTIEEL hypothetical protein 1542 (32/70) ENKGYVLVSDGFPAGATFDNDDNTTQIYTVVL LJ0047 [Lactobacillus johnsonii NCC 533] 26. ref|ZP 04063040.1| Sbjct 44% ITYVDQTTGQTLANDQVGGKSGEAINYSTADKIKYY adhesion exoprotein 1429 (31/70) EDRGYVLVSDEFPKGAHFDNDASVDQIWTVTL [Streptococcus salivarius SK126] 27. refIZP 04061224.1| Sbjct 44% ITYVDQTTSQTLANDQVGGKSGEAINYSTADKIKYYE adhesion exoprotein 223 (31/70) DRGYVLVSDEFPTGAHFDNDASVDQTWTVTL [Streptococcus salivarius SK126] 28. ref|ZP 03073062.1| Sbjct 44% VNYVDQDNNNAQIATSGNLTGKPGSVINYSTADQIK LPXTG-motif cell wal1 1198 (31/70) QLEAQGYVLVSDGFPAGAVFDNDDNTTQTYTVVL anchor domain protein [Lactobacillus reuteri  100-23] (″LPXTG″ disclosed as SEQ ID NO: 84) 29. ref|ZP 08229673.1| Sbjct  40% VSYVDDTTGKTLKTDSISGTTGSKSSYSTSGNIADYK mucus binding protein 16 (28/70) KHGYELVTDGYPADLTFDNDDKTDQNFTV [Leuconostoc argentinum KCTC 3773] 30. ref|ZP_08574918.1| Sbjct 41% VSYVDDTTGKTLKTDSISGTTGSKSSYSTSGNIADYK cell surface protein 732 (29/70) KQGYELVTDGYPADLTFDNDDTTDQNFTV precursor [Lactobacillus coryniformis subsp. torquens KCTC 3535] 31. ref|ZP 03073481.1| Sbjct 44% VNYVDQDNNNAQIATSGNLTGKPGSVINYSTADQIK LPXTG-motif cell wall  3821 (31/70) QLEDQGYVLVSDGFPAGAVFDNDDNTTQTYTVVL anchor domain protein [Lactobacillus reuteri 100-23] 32. ref|YP 004727441.1| Sbjct 44% ASVTYRDETSGSILETVALAGKSGEAINYSTAERIKH hypothetical protein 601 (31/70) YQDLGYALVTDGYPAGASFDLDSTVDQAWTVSF SALIVB_0614 [Streptococcus salivarius CCHSS3] 33. ref|YP 001727229.1| Sbjct 40% VSYVDDTTGKTLKTDSISGTTGSKSSYSTSGNIADYK mucus binding protein 688 (28/70) KQGYELVTDGYPADLTFDNNDTTDQNFTV [Leuconostoc citreum KM20] 34. ref|ZP 04642914.1| Sbjct 43% DGANKQLATSGDLTGKSGSEISYSTADQIKKLINQG adhesion exoprotein 2768 (30/70) YVLKNDGFPAGAVFDNDDSKNQVFYVDF [Lactobacillus gasseri 202-4] 35. ref|ZP_06261711.1| Sbjct 43% DGANKQLATSGDLTGKSGSEISYSTADQIKKLINQG gram-positive signal 2818 (30/70) YVLKNDGFPAGAVFDNDDSKNQVFYVDF peptide protein, YSIRK family [Lactobacillus gasseri 224-1] 36. ref|YP 813898.1| Sbjct 43% DGANKQLATSGDLTGKSGSEISYSTADQIKKLINQG adhesion exoprotein 2830 (30/70) YVLKNDGFPAGAVFDNDDSKNQVFYVDF [Lactobacillus gasseri ATCC 33323] 37. ref|ZP 07712941.1| Sbjct 43% DGANKQLATSGDLTGKSGSEISYSTADQIKKLINQG putative mucus binding 2124 (30/70) YVLKNDGFPAGAVFDNDDSKNQVFYVDF protein [Lactobacillus gasseri MV-22] Length = 2986 38. ref|YP 004033545.1| Sbjct 43% AKVAYIDDKTGKTLKTDSLTGVTNAKSGYTTADSIKT mucus binding protein 612 (30/70) YQALGYKLVSDDTKGAEIVFDNEDGKDQSYTVHF [Lactobacillus delbrueckii subsp. bulgaricus ND02] 39. ref|ZP 05549219.1| Sbjct 43% VNYIDSDEGNKVITTSGNLSGKAGSTIDYSTKSTIADL adhension protein 2301 (30/70) ENKGYVLVNDGFPAGAKFDSDDNTTQIFTVVL [Lactobacillus crispatus  125-2-CHN] 40. ref|ZP 08047859.1| Sbjct 43% ASVTYRDETGGSTLETVSLAGKSGEAVGYSTAERIK putative mucus binding 334 (30/70) HYQDLGYVLVTDGYPAGTTFDLDSTVDQAWTVSF protein [Streptococcus sp. C150] 41. ref|ZP 04061106.1| Sbjct 41% ASVTYRDETSGSTLETVALAGKSGEAVNYSTADRIK MucBP domain protein 760 (29/70) HYQDLGYVLVTDGYPAGATFDLDSTVDQAWTVSF [Streptococcus salivarius SK126] 42. ref|ZP 07644834.1| Sbjct 37% IRYVSTNGNQVLKTDEVTGKSGEAIAYSTTSQINEFK Mlp [Streptococcus 429 (26/70) KQGYKLVSDEFTAGGAKVYDYDTARDQVYTVTL mitis NCTC 12261] 43. ref|ZP 08417090.1| Sbjct 39% IAYIDKTTGKQLALDPITGHSDESSTYTTADKIAAYEA mucus binding protein 4532 (27/70) AGYVLVSDGYPGANFTFDREDDYDQTYEVIL [Weissella cibaria KACC 11862] 44. ref|YP 004727470.1| Sbjct 41% ITYIDETTGAYLVSDQLTGELGEAIEYGTATRIKTFKD hypothetical protein 231 (29/70) MGYELIQDEFPKDAIFDDKDIDDQEWFVLL SALIVB_0643 [Streptococcus salivarius CCHSS3] 45. ref|ZP_04008293.1| Sbjct 40% VTYVDDKTGKTLKVDNLNGVTSAKSGYTTKAAIDTY conserved hypothetical 86 (28/70) TGLGYTLVSDDTNGNEWFDNDDSNDQAFTV protein [Lactobacillus  johnsonii ATCC 33200] 46. ref|YP 193899.1| Sbjct 39% VNYIDADEGNKVIISSGNLIGKAGDKVDYNTSDTIKNL mucus binding protein 2251 (27/70) ENKGYVLVHNGFPDGVTFDNDDSTIQTYTVIL [Lactobacillus acidophilus NCFM] Length = 2650 47. ref|ZP 04021706.1| Sbjct 39% VNYIDADEGNKVIISSGNLIGKAGDKVDYNTSDTIKNL mucus binding protein 2251 (27/70) ENKGYVLVHNGFPDGVTFDNDDSTIQTYTVIL [Lactobacillus acidophilus ATCC 4796] 48. ref|ZP_04061119.1| Sbjct 40% ITYIDETTGAYLVSDQLTGELGEAIEYGTATRIKTFKD MucBP domain protein 231 (28/70) MGYDLIQDEFPKDAIFDDKDIDDQEWFVLL [Streptococcus salivarius SK126] 49. ref|YP 004034456.1| cell surface protein Sbjct 41% VSYVDDTTGKTLKTDSISGITGSKSSYSTSGSIADYK [Lactobacillus 452 (29/70) KQGYELVTDGYPADLTFDNDDTTDQNFTV delbrueckii subsp. bulgaricus ND02] 50. ref|ZP 05863780.1| Sbjct 41% VSYVDDTTGKTLKTDSISGTTGSKSSYSTSGSIADYK conserved hypothetical 410 (29/70) KQGYELVTDGYPADLTFDNDDTTDQNFTV protein [Lactobacillus fermentum 28-3-CHN] 51. ref|YP 001843489.1| Sbjct 41% VSYVDDTTGKTLKTDSISGTTGSKSSYSTSGSIADYK hypothetical protein 533 (29/70) KQGYELVTDGYPADLTFDNDDTKDQNFTV LAF_0673 [Lactobacillus fermentum IFO 3956] 52. ref|ZP 08047833.1| Sbjct 41% VTYVDGTTRKKLEVVDLLGKSGEVIDYSTIERIKYYS putative mucus binding 1019 (29/70) DRGYTLLADGFTNGVIFDGDSHVDQNFMVTL protein [Streptococcus sp. C150] 53. ref|ZP_05863779.1| Sbjct 41% VSYVDDTTRKTLKTDSISGTTGSKSSYSTSGSIADYK predicted protein 30 (29/70) KQGYELVTDGYPADLMFDNDDTTDQNFTV [Lactobacillus fermentum 28-3-CHN] 54. ref|ZP 07059088.1| Sbjct 44% IlYVDETTGKALETATVDGKYNESINYSTADKIKYYES conserved hypothetical 1860 (31/70) LGYELVKDGYTAG-KF--GETTKTFY-VIF protein [Lactobacillus gasseri JV-V03] 55. ref|ZP 04644067.1| Sbjct 34% IVYVDETTGKELERATVDGKYNETINYSTADKIKYYE putative cell surface 1440 (24/70) SLGYELVKDGYTGGE protein [Lactobacillus gasseri 202-4] 56. ref|ZP 07712160.1| Sbjct 32% LDNEGQQITSSGPLIGKPNENITDLYSTSIPLAGLEKA putative mucus binding 485 (22/70) GYHVIFNNFDGNNKIQKFDGND LTTQVFTV protein [Lactobacillus gasseri MV-22] 57. ref|ZP 04643870.1| Sbjct 32% LDNEGQQITSSGPLIGKPNENITDLYSTSIPLAGLEKA adhesion exoprotein 488 (22/70) GYHVIFNNFDGNNKIQKFDGND LTTQVFTV [Lactobacillus gasseri 202-4]

In a particular embodiment, a polypeptide of the invention has the sequence SEQ ID NO: 3 or SEQ ID NO: 4 or has an amino-acid sequence comprising or consisting of any one of SEQ ID NO: 23 to 57 or a fragment thereof.

In a specific embodiment, a polypeptide of the invention is a fragment of contiguous amino-acid residues of at least 10 amino-acid residues, in particular 17 amino-acid residues, of SEQ ID NO: 3 or SEQ ID NO: 4 or of any one of SEQ ID NOS 5 to 16 or SEQ ID NOS 19 to 57.

The inventors have also synthesized and characterized shorter peptides according to the invention, identified by the term MUB₄₀, which span the entire MUB₇₀ sequence. Their sequences are provided in Table 3.

TABLE 3 MUB₄₀ (SEQ ID NOS 58, 59, 60 and 61) operating sequences. See also FIG. 17 SEQ ID NO: References Sequence 58 MUB40-1, used for probe TAEGIKKFEGDGYELFKDNFPAGEKFDNDDTNDQFYTVIF MUB40-Cy5#1 59 MUB40-2, used for probe GYTDETIPYSTAEGIKKFEGDGYELFKDNFPAGEKFDNDD MUB40-Cy5#2 60 MUB40-3, used for probe DQMLRQDDLDGYTDETIPYSTAEGIKKFEGDGYELFKDNF MUB40-Cy5#3 61 MUB40-4, used for probe VHVQYIDGETDQMLRQDDLDGYTDETIPYSTAEGIKKFEG MUB40-Cy5#4

In a particular embodiment, a polypeptide of the invention has the sequence SEQ ID NOS 58 or 59 or 60 or 61 or has an amino-acid sequence comprising or consisting of any one of SEQ ID NOS 58 to 61 or a fragment thereof.

According to a particular embodiment, synthesized peptides MUB₄₀₋₁ to MUB₄₀₋₄ of the invention (SEQ ID NOS 58, 59, 60, 61) have an additional Cysteine residue at their respective N-terminal extremities (SEQ ID NOS 62, 63, 64, 65). These shorter peptides proved to be functional as human mucus-binding peptides, as detailed herein.

A polypeptide of the invention advantageously lacks or is devoid of hydrophobic domain(s). According to a preferred embodiment, it does not penetrate into living cells, especially eukaryotic cells and in particular it does not penetrate into such cells of human colon, e.g. goblet cells. According to a particular embodiment however, a polypeptide of the invention possesses globet-cells binding properties.

However in a particular embodiment, polypeptide(s) of the invention penetrate into fixed cell(s).

According to a particular embodiment, polypeptide(s) of the invention is/are not toxic to cells. Non-limitative examples of cells that might be impervious to the polypeptides of the invention are epithelial cells, especially human epithelial cells, myeloid cells, especially human myeloid cells, Embryonic Stem (ES) cells, especially human Embryonic Stem (ES) cells, dendritic cells, especially mouse dendritic cells.

However, it was found that, according to a particular embodiment, the polypeptides of the invention target components found at the level of neutrophile granules, especially fixed neutrophile granules, which are not yet characterized. In vitro incubation of the polypeptide with living neutrophiles, or analysis of fixed neutrophiles, therefore allows the detection of degranulation events.

In a particular embodiment, a polypeptide of the invention has an additional Cysteine residue at its N-terminal extremity. The presence of a free Cysteine residue may be of interest to enable attachment of additional moieties, especially markers or labels or other active groups.

However, according to another particular embodiment, no specific amino-acid residue is required at the N-terminal extremity of a polypeptide of the invention to achieve attachment of additional moieties, since any amino-acid carboxy group or another chemical group of a polypeptide of the invention can be used to this end.

In a particular embodiment of the invention, the polypeptide comprises or is constituted by L amino acid residues.

In a particular embodiment, the polypeptides comprise or are fully constituted by D-amino acids (excluding the chiral form of amino acids naturally synthesized by living organisms, which is the L-form), or comprise or are fully constituted by modified aminoacids. Such modifications might help preventing proteolytic cleavage by active enzymes, especially when the polypeptide is administered in vivo.

According to a particular embodiment, polypeptide(s) of the invention is/are labelled, especially by coupling with a fluorophore such as Cy5, Cys5.5, or a biotin. A Cy5-labelled MUB₇₀ polypeptide (or respectively, a Cy5-labelled MUB₄₀ polypeptide) is therefore referred to as MUB₇₀-Cy5 or Cy5-MUB₇₀ (respectively MUB₄₀-Cy5 or Cy5-MUB₄₀) within the present disclosure.

According to a particular embodiment, the invention enables the detection or the monitoring of mucus production and/or mucus composition in human or animal body(ies), especially the detection or the monitoring of human colonic or intestinal mucus. According to a particular embodiment, the invention makes use of labeled polypeptide(s) as probe(s), especially as physiological labeled probe(s) for staining Muc2 protein(s) contained in mucus layer(s) of cell or tissue sample(s).

According to a particular embodiment, the invention makes use of labeled polypeptide(s) as probe(s), especially labeled probe(s) for staining fixed or living neutrophile(s). Staining living neutrophile(s) is preferably achieved in vitro.

It has further been observed by the inventors that Muc2 proteins are also expressed in other tissues of the human body, either when said tissues are in a healthy state or to the contrary when they reflect a pathological state.

Hence, the polypeptides of the invention may be used for detection or monitoring of mucus production and/or composition, in other tissues such as lung tissue or epithelial tissue.

In a particular embodiment, polypeptide(s) of the invention is/are associated in a molecule with a reporter or a carrier molecule or with an active molecule such as drug(s) (i.e. anti-inflammatory molecule(s)) or enzyme(s) such as DNase or chitinase (e.g. cystic fibrosis context), or fragments thereof.

The polypeptides and molecules of the invention can be prepared by conventional routes, in particular chemically synthesized or engineered through biotechnological methods.

In a particular embodiment wherein the polypeptide of the invention has the sequence SEQ ID NO: 3 or SEQ ID NO: 4 or a continuous fragment thereof, in particular a fragment thereof of about contiguous 40 amino-acid residues, especially as found within the C-terminal extremity of SEQ ID NO: 3 or SEQ ID NO: 4, chemical synthesis is achieved through Solid-Phase synthesis, especially trough Fmoc-SPPS, including steps of coupling with Fmoc-Asp(OtBu)-(Dmb)Gly-OH dipeptides when the synthesis reaches the positions 29 and/or 50 and/or 63 in reference to the C-terminus of SEQ ID NO: 3.

Additionally, said solid-phase synthesis can include steps of incorporation of pseudoproline dipeptides when the synthesis reaches positions 10 and/or 40 in reference to the C-terminus of SEQ ID NO: 3.

This synthesis is illustrated in the examples and can be similarly used for other polypeptides having analogous amino-acid composition, in particular peptides shorter than the MUB70 peptide and having at least partly an amino-acid composition that is analogous to MUB70 peptide composition.

Accordingly, the specific features and properties detailed herein with respect to the MUB70 peptide are also applicable to MUB70 analogous peptide(s), (having similarity in amino-acid composition, or encompassing MUB70 fragment(s), or MUB70 fragment(s)), as disclosed herein.

When polypeptide(s) of the invention are prepared in recombinant cells, these cells are recombined with a polynucleotide expressing the polypeptide, using nucleic acid expression systems such as plasmid vectors.

Therefore, the invention also encompasses nucleic acid molecule(s) encoding polypeptidic sequence(s) of isolated polypeptide(s) as described herein and nucleic acid expression system(s), especially vector(s) comprising such nucleic acid molecule(s) under expression control sequences.

According to a particular embodiment, production of isolated polypeptide(s) of the invention is achieved through the transfection of such vector(s) in cell(s) such as E. coli cell(s) or eukaryotic cells, including yeast cells, insect cells or mammalian cells, the culture of said cell(s) and the recovery of the protein result of the culture, especially the recovery of the polypeptide(s) of the invention.

According to a particular embodiment, production of isolated polypeptide(s) of the invention is done using a MGMT-based method for obtaining high yield of recombinant protein expression, as disclosed in patent application WO2012/076715.

In such a particular embodiment, a vector of the invention may comprise a nucleotide sequence encoding in a single open reading frame, from 5′ to 3′:

-   -   a) a peptidic secretion signal which is functional in insect         cells, in particular S2 Drosophilia insect cells;     -   b) a 6-methylguanine-DNA-methyltransferase enzyme (MGMT, EC         2.1.1.63) or a mutant or a fragment thereof having at least 80%         of the catalytic activity of the native MGMT protein;     -   c) a polypeptide of the invention, as disclosed herein.

In a particular embodiment, production of isolated polypeptide(s) of the invention is thus achieved through the transfection of the vector(s) described herein, in particular MGMT-based vector(s), in S2 Drosophilia insect cell(s).

The invention also encompasses cell(s) or population of cells, in particular S2 Drosophilia insect cells, comprising a nucleic acid molecule or a vector as described herein, especially for use in a method of production of isolated or purified polypeptide(s) of the invention.

The invention also relates to composition(s) comprising polypeptide(s) of the invention, in particular pharmaceutical composition(s) when the polypeptide is associated with an active ingredient having a therapeutic effect, said composition comprising if necessary pharmaceutically acceptable excipient(s), such as carrier(s) and/or adjuvant(s),

According to a particular embodiment, the molecule(s) derived from theses polypeptides according to the invention might be used in a method for manufacturing a medicament, when a step of association of a polypeptide of the invention with a biologically active molecule is performed, and therefore used in a method of therapy practised on human or animal body(ies), in particular for treating a disease selected form the following group, or its symptom(s): neoplasic disease(s), including mucinous carcinoma(s), gastric cancer(s) or colorectal cancer(s), especially colon cancer(s), cystic fibrosis disease, intestine inflammatory disease(s) such as inflammatory bowel disease (IBD) and ulcerative colitis.

The invention thus also relates to the use of a polypeptide of the invention, as a probe or marker for staining living cell(s) or tissue(s) in in vivo, ex vivo, specifically in in vitro experiments, in particular in live microscopy experiments. Live microscopy encompasses for example the use of widefield microscopy on living cells (for example HT29-MTX cells stained with Cy5-MUB₇₀), 2-photons microscopy (for example on human colon ex vivo sample stained with Cy5-MUB₇₀), or 3D animal analysis (Xenogen, Ivis, Cy5-MUB₇₀), (Fluoptics, Cy5.5-MUB₇₀), or spectral imaging (for example: coloscopy).

In a particular embodiment, the invention relates to the use of a labelled polypeptide as a probe or marker for staining Muc2 protein(s) contained in mucus layer of a cell or tissue sample, especially human colonic or intestine tissue sample.

In a particular embodiment, the invention relates to the use of a polypeptide as a physiological labelled probe to detect in vitro interaction with human colonic mucus in the adhesive mucus layer of colonic tissue sample and/or to detect in vitro interaction with globet cells.

By “physiological labelled probe”, it is meant a probe that is non-harmful, i.e. non-toxic, and well-tolerated by cells or biological tissues.

In a particular embodiment, the invention relates to the use of a polypeptide to detect in vitro mucus production or mucus composition in human colon, said use comprising contacting said polypeptide with a sample of colonic tissue comprising adhesive mucus layer and goblet cells and detecting stained mucus.

In another particular embodiment, the invention relates to a polypeptide of the invention, which is labelled, for use as a probe for in vivo detection of mucus production or mucus composition in human intestine, especially colon or other compartments such as lung tissue, nasal tissue or stomach tissue.

The invention therefore relates to the use of a polypeptide or of a composition comprising the same, as a probe for staining mucus potentially containing Muc2 protein(s) or exhibiting variations in Muc2 protein(s) expression that could provide information on a change in mucus production or in mucus composition.

According to a particular embodiment, the observed mucus is colonic mucus, for example in human, rabbit or guinea pig samples as well as human cell lines producing a mucus layer samples.

According to a particular embodiment, the observed mucus is human colonic carcinoma mucus.

According to a particular embodiment, stained mucus-producing cells are eukaryotic cell(s), including intestine mucus cells, such as goblet cells.

The probes of the invention are preferably non-toxic to cells, which are preferably impervious to said probes.

However, according to another specific embodiment, the invention is also directed to the use of a polypeptide of the invention, in particular MUB₇₀ and/or MUB₄₀ polypeptides or polypeptides sharing identity with MUB₇₀ and/or MUB₄₀ polypeptides, or fragments thereof, as marker of degranulation event(s) in neutrophiles, especially an in vitro marker of degranulation event(s) in neutrophiles

Detection in vitro of mucus production or mucus composition in human colon might serve as a basis for comparisons between samples, and therefore might serve to analyse or detect or monitor variations or modulations of mucus production or mucus composition in an human or animal body. With this respect, it has been observed that Muc2 protein is naturally expressed and secreted in intestine mucus as a major component of said mucus in healthy tissue, especially in healthy colonic tissue. It has also been observed that Muc2 protein is not expressed in healthy trachea or lung tissues, and in healthy stomach tissues. A change in Muc2 expression in these tissues may thus provide information on the tissue status.

Muc2 expression modulation is also observed in gastric cancer (increased), in ductal adenocarcinoma, in cystic fibrosis (increased), in cystic fibrosis transmembrane conductance regulator model, especially with respect to lung tissues, nasal tissue, goldbladder tissue, pancreas tissue. Muc2 expression modulation is also observed in Inflammatory Bowel Diseases (IBD) such as ulcerative colitis and Crohn disease.

Also, Muc2 glycosylation profile is modulated in colonic diseases such as ulcerative colitis or colorectal carcinoma.

Accordingly, another object of the invention is therefore the use of a polypeptide or of a composition of the invention for in vitro detecting or monitoring any one of the following disease conditions: neoplasic disease(s), including mucinous carcinoma(s), in particular colonic mucinous carcinoma(s), gastric cancer(s) or colorectal cancer(s), especially colon cancer(s), (but also lung, stomach, breast, prostate, or bile ducts cancers) cystic fibrosis, intestine inflammatory disease(s) such as inflammatory bowel disease (IBD) and ulcerative colitis.

The invention also relates to a method for manufacturing a medicament comprising a step of association, especially, coupling, grafting or fusing a polypeptide of the invention with a biologically active molecule such as a drug or an enzyme.

Polypeptide(s), composition(s) or medicament(s) resulting from a polypeptide associated with a biologically active molecule can be used in a method of therapy practised on a human or animal body.

The invention thus encompasses the use of polypeptide(s), composition(s) or medicament(s) resulting from a polypeptide associated with a biologically active molecule for use in treating a disease selected from the following group, or its symptom(s): neoplasic disease(s), including mucinous carcinoma(s), in particular colonic mucinous carcinoma(s), gastric cancer(s) or colorectal cancer(s), especially colon cancer(s) but also lung, stomach, breast, prostate, or bile ducts cancers, cystic fibrosis, intestine inflammatory disease(s) such as inflammatory bowel disease (IBD) and ulcerative colitis.

Other examples and features of the invention will be apparent when reading the examples and the figures, which illustrate the experiments conducted by the inventors, in complement to the features and definitions given in the present description.

LEGEND OF THE FIGURES

FIG. 1. MUB₇₀ identification in L. reuteri. (A) MucBP diversity illustrated comparing L. reuteri (Genbank AF120104) and L. plantarum (Ip_1229). (B) Representation of MUB₇₀/MucBD 13 repeats of L. reuteri AF120104 (SEQ ID NO: 5 to SEQ ID NO: 16). (C) Sequences comparison between L. reuteri AF120104 (SEQ ID NO: 11) protein sequence and homologous proteins in L. gasseri (ZP_07711585) (SEQ ID NO: 19), L. johnsonii (ZP_04008294.1) (SEQ ID NO: 20), L. fermentum (YP_001843489.1) (SEQ ID NO: 21) and L. acidophilus (SEQ ID NO: 22) are performed using ClustalW software. MUB₇₀ sequence and conserved amino acid are highlighted in light gray. MucBD (pfam 06458) sequence and conserved amino acids are highlighted in dark gray. Perfect match over all compared sequences are identified with an asterisk. Good matches are identified with a double dot or a dot.

FIG. 2. MUB₇₀ chemical synthesis and biochemical analysis of trimerization property. (A) RP-MPLC MUB₇₀ final purification result. (B). SDS-PAGE visualization of the trimeric form of biot-MUB₇₀ performed after incubation of the peptide in Tris 25 mM pH=4 and pH=8. (C) Characterization of biot-MUB₇₀ by gel filtration chromatography on Superdex 200 5/150 GL column. The elution profile of biot-MUB₇₀ is shown at 280 nm.

FIG. 3. Cy5-MUB₇₀ colonic mucus binding property. (A) HT-29 MTX living cells were incubated for 2 h with Cy5-MUB₇₀ in a serum-free media. The resulting fluorescent signal (red) was visualized at the surface of the cell layer using an epifluorescent microscope. Z-projection, performed using ImageJ software, allowed 3D localization of Cy5-MUB₇₀ fluorescence signal in the mucus layer. Bar is 10 μm (B) MPE and SHG imaging of the binding of Cy5-MUB₇₀ to the human colonic mucus. 3D reconstruction (isosurface representation) shows the colonic epithelium covered by the mucus layer (up to 1 000 μm) after 90 min of incubation with Cy5-MUB₇₀. Human tissue autofluorescence is detected in the same red channel as Cy5.

FIG. 4. Cy5-MUB₇₀ is specifically binding to the glycosylated moiety of Muc2 secreted in the colon mucus layer. (A) Immunodetection of Muc2, Muc5ac, Muc5b and Muc6 (dotblot analysis) on human mucus extracts eluted after a pulldown assay performed with biot-MUB₇₀ on avidin conjugated beads (see Methods). Biotin is used as a negative control. Immunodetection of Muc2 (dotblot analysis) on deglycosylated mucus extracts eluted after a pulldown assay performed with biot-MUB₇₀ on avidin conjugated beads. Non-deglycosylated mucus extract is used as a positive control. (B) Co-localization of Muc2 (green) and Cy5-MUB (blue) observed on fixed (Carnoy) human colon samples. Actin is stained in red (Phall.RRX). Observations are performed using a confocal microscope. Bars is 20 μm.

FIG. 5. MUB₇₀ (SEQ ID NOS 3 or 4) synthesis strategies description. Operating sequences for designed synthesis 1 and 2, where secondary amino acid surrogates are underlined (pseudoproline dipeptides) or bold (Dmb dipeptides). Proline residues are in italic.

FIG. 6. MUB₇₀ analytical HPLC profiles in TFA conditions. (A) Crude synthesis 1. MUB₇₀ was detected as a major peak (around 8% by area integration) (B) Crude synthesis 2. Optimisation of the synthesis adding three Dmb dipeptides able to reduce aspartimide side reaction and two pseudoproline dipeptides (see Methods). MUB₇₀ was detected as a major peak representing 25% of the area integration. (C) Monomeric MUB₇₀ after a first step of purification (in acidic conditions, pH 6.5). (D) MUB₇₀ after a second step of purification (neutral conditions) and (E) MUB₇₀ after a third step of purification (neutral conditions) allowed to yield a purity above 90% on MUB₇₀ oligomers.

FIG. 7. Biochemical properties of MUB₇₀. (A) MUB₇₀ total charge was calculated using Protein Calculator program (Scripps website). (B) Kytes and Doolittle hydropathy profile of MUB₇₀ was generated using ExPASy bioinformatical tools. (C) Validation of biot-MUB₇₀ purity by gel filtration chromatography on Superdex 200 5/150 GL column. (D) Partition coefficients (K_(av)) of the standard proteins (ferritin, 440 kDa; aldolase, 158 kDa; ovalbumin, 43 kDa; ribonuclease A, 13.7 kDa; aprotinin, 6.5 kDa) were calculated according to K_(av)=(V_(e)−V₀)/(V_(t)−V₀) (V_(e), elution volume; V₀, void volume; V_(t), total volume of the gel bed) and plotted against the corresponding molecular masses. The molecular mass of biot-MUB₇₀ calculated using the calibration curve equation: log(M_(r))=3.12-3.1 K_(av).

FIG. 8. (A) Cell toxicity of Cy5-MUB₇₀ tested on HT-29-MTX and Hela epithelial cells. Cell survival was assessed using Sytoxgreen dye on cultures exposed to 1 μg/mL Cy5-MUB₇₀ from 0 to 10 h, as indicated. NS indicates P>0.05 (Student's T-test). (B) Rabbit colonic and ileal mucus staining on fixed tissues (PFA 4%), using Cy5-MUB₇₀ (1 μg/mL) (blue). Actin is stained in red (Phall.-RRX). Bar is 50 μm. (C) Human ex vivo colon sample was incubated for 2 h with 1 μg/mL Cy5-MUB₇₀ in a serum-free media. Resulting fluorescent staining was assessed using a two-photons microscope (see Methods). Z-projection, performed using ImageJ software, allows 3D localization of Cy5-MUB₇₀ fluorescence signal. Bar is 100 μm. Colon scheme: firmly (f) and loosely (l) attached colonic mucus layers are represented at the surface of the epithelium (e). (D) Kinetics of colonic mucus with Cy5-MUB₇₀. 3D reconstruction (isosurface representation) shows the colonic epithelium covered by the mucus layer (up to 1 000 μm) after 60, 90 and 120 min of incubation with Cy5-MUB₇₀. Human tissue autofluorescence is detected in the same red channel as Cy5.

FIG. 9. (A) Co-localization of Muc2 (green) and Cy5-MUB (blue) performed by immunofluorescent detection on human mucus extract collected on ex vivo tissues using an epifluorescent microscope. Bar is 50 μm. (B) Co-localization of Muc2 (green) and Cy5-MUB (blue) observed on fixed (PFA 4%) rabbit colon samples. Actin is stained in red (Phall.RRX). Observations are performed using a confocal microscope. Bars is 40 μm.

FIG. 10. (A) Human mucus negative staining using Cy5 (blue). Muc2 (green) is used as a positive control. Observations were performed by immunofluorescent detection on human mucus extract collected on ex vivo tissues using an epifluorescent microscope. Bar is 50 μm. (B) Immunodetection of FCGBP (dotblot analysis) on human mucus extracts eluted after a pulldown assay performed with biot-MUB₇₀ on avidin conjugated beads (see Methods). Biotin is used as a negative control. (C) Immunodetection of FCGBP (dotblot analysis) on deglycosylated mucus extracts and eluted after a pulldown assay performed with biot-MUB₇₀ on avidin conjugated beads. Non-deglycosylated mucus extract is used as a positive control.

FIG. 11. Mucus staining using Cy5-MUB₇₀ on fixed tissues. (A) Guinea pig colon, (B) rabbit ileum and (C) mouse colon were fixed in PFA 4%. Immunofluorescent staining was performed using Cy5-MUB₇₀ (1 μg/mL) (blue). Actin is stained in red (Phall.-RRX), Muc2 is stained in green (α-Muc2). Observations were performed using a confocal microscope. Bar is 50 μm.

FIG. 12. ClustalW sequence alignments of MUB domain repeats 1 to 13 found in L reuteri AF120104 and disclosed in Table 1 (SEQ ID NO: 5 to SEQ ID NO: 16). Figure discloses SEQ ID NOS 11, 11, 10, 12-14, 9, 15, 6, 5, 7, 8 and 16, respectively, in order of appearance.

FIG. 13. Staining of individual neutrophiles (white blood cells) in rabbit ileum sub-mucosa. Cy5-MUB70 was incubated on PFA 4% fixed tissues. Signal was colocalized with an α-elastase (PMN) signal. (Primary antibody is α-elastase (PMN) 1:400 and secondary antibody is anti-mouse GFP 1:400, MUBCys5 1:400, Phalloidin-RRX 1:400). This result indicates that Cy5-MUB70 is binding specifically a neutrophile component. In particular, granules staining is achieved.

FIG. 14. Staining of individual neutrophiles (white blood cells) in human blood sample. Cy5-MUB70 was incubated on ethanol 100% fixed blood sample. Signal was detected as diffused in neutrophile cytoplasm, due to membrane solubilisation following alcoholic fixation. (Details are provided on the Figure). This result confirms that Cy5-MUB70 is binding specifically a neutrophile component. In particular, granules staining is achieved.

FIG. 15. Staining of individual neutrophiles (white blood cells) purified from fresh human blood sample. Cy5-MUB70 was incubated on PFA 4% fixed neutrophiles (PFA treatment for 15 min, wash 3 times in PBS). Signal was detected as dots distributed in neutrophile cytoplasms. (Staining with Dapi 1:1000 and EB1C5 1:1000 in PBS+10% FCS+0.1% Saponin). This result indicates that Cy5-MUB70 is binding specifically a neutrophile granule component. In particular, granules staining is achieved.

FIG. 16. GenBank data under access number AF120104.1 relating to the Mub protein sequence of L. reuteri and the corresponding nucleic acid sequence (SEQ ID NOS 17 and 18).

FIG. 17. MUB₄₀ operating sequences (with Cysteine residues at N-terminal extremities) synthesis strategies description (SEQ ID NOS 62, 63, 64 and 65). Operating sequences for designed synthesis of peptides having SEQ ID NOS 58, 59, 60 and 61 as described herein, with Cysteine residues at their N-terminal extremities, where secondary amino acid surrogates are underlined (pseudoproline dipeptides) or in bold (Dmb dipeptides). Proline residues are in italic bold.

FIG. 18. HPLC analysis of the Cy5-MUB40-1 peptide. Retention time of 13.927 min and Molecular weight of 5549 were obtained.

FIG. 19. HPLC analysis of the Cy5-MUB40-2 peptide. Retention time of 11.107 min and Molecular weight of 5547 were obtained.

FIG. 20. HPLC analysis of the Cy5-MUB40-3 peptide. Retention time of 11.624 min and Molecular weight of 5588 were obtained.

FIG. 21. HPLC analysis of the Cy5-MUB40-4 peptide. Retention time of 9.828 min and Molecular weight of 5501 were obtained.

FIG. 22. Schematic description of the Cy5-MUB40-1, Cy5-MUB40-2, Cy5-MUB40-3, Cy5-MUB40-4 peptides (SEQ ID NOS 62 to 65). Fluorescent staining of human colonic mucus was performed by the addition of 1 μg/mL of the corresponding Cy5-conjugated peptides with Phalloidin-RRX (1:100) on formol fixed, paraffin embedded samples. Image acquisition was performed using a fluorescent confocal microscope (see Methods).

FIG. 23 Comparative staining analysis of human colonic goblet cells using Cy5-MUB70 and Cy5-MUB40-1. Fluorescent staining of human colonic mucus was performed by the addition of 1 μg/mL of the corresponding Cy5-conjugated peptides with Phalloidin-RRX (1:100) on formol fixed, paraffin embedded samples. Image acquisition was performed using a fluorescent confocal microscope (see Methods).

FIG. 24. Comparative human colonic mucus staining using MUB70-Cy5 on healthy tissues and mucinous carcinomas (Coic et al, JBC, 2012 (41)). Fluorescent staining of human colonic mucus was performed by the addition of 1 μg/mL of the corresponding Cy5-conjugated peptides with Phalloidin-RRX (1:100) on formol fixed, paraffin embedded samples. Image acquisition was performed using a fluorescent confocal microscope (see Methods).

FIG. 25. Schematic description of the MUB70-SNAP cloning strategy. S2 insect cell line was stably transfected using a DeSNAPuniv-MUB70 plasmid in order to allow the overexpression and the secretion of MUB70-SNAP in the cell culture media (see Methods). Figure discloses SEQ ID NOS 85-88, 86, and 89, respectively, in order of appearance.

FIG. 26. MUB70-SNAP secretion detection in S2 insect cell lines stably transfected with pDeSNAPuniv-MUB70 was induced by the addition of 5 μg/mL CdCl₂. MUB70-SNAP was detected in 10 μL of the cell culture media by Western blot using an anti-SNAP antibody. The detection of the secretion of SNAP using an empty pDeSNAP vector was used as a control.

FIG. 27. MUB70 protein production in S2 cells. MUB70-SNAP production in stable transfected S2 insect cells was performed in 1 L of culture media. Following two purification steps (see Methods) the gel filtration fractions were loaded onto a SDS Page gel further stained by Coomassie. 25 mg of MUB70-SNAP were obtained from 1 production batch.

FIG. 28. MUB70-SNAP is not stable at 4° C. as after 3 months of storage in these conditions, some degradation products are detected by gel filtration (see Methods, second purification step).

FIG. 29. Identification of Muc2 in neutrophile granules using MUB70-Cy5. Human neutrophil (PMN) granule staining using Cy5-MUB70. PMN were purified from healthy donor blood samples and fixed in the presence of 4% PFA. Fluorescent staining of human colonic mucus was performed by the addition of 1 μg/mL of Cy5-MUB70 (Red) with Dapi (1:100) (Blue) and 1:200 anti-Muc2 antibody (Green). Image acquisition was performed using a fluorescent confocal microscope (see Methods).

FIG. 30. Identification of Muc2 in neutrophile granules using MUB70-Cy5. Activated (+Shigella flexneri) human neutrophil (PMN) granule staining using Cy5-MUB70. PMN were purified from healthy donor blood samples and incubated with Shigella flexneri (MOI 20) during 15 min prior fixation in the presence of 4% PFA. Fluorescent staining of human colonic mucus was performed by the addition of 1 μg/mL of Cy5-MUB70 (Red) with Dapi (1:100) (Blue) and 1:200 anti-Muc2 antibody (Green). Image acquisition was performed using a fluorescent confocal microscope (see Methods). PMN activation (addition of Shigella flexneri) leads to an increase of the Muc2 accumulation in the granules.

FIG. 31. Identification of Muc2 in neutrophile granules. Human neutrophil (PMN) granule staining using Cy5-MUB40-1, Cy5-MUB40-2, Cy5-MUB40-3, Cy5-MUB40-4 peptides. Schematic description of the Cy5-conjugated peptides. PMN were purified from healthy donor blood samples and fixed in the presence of 4% PFA. Fluorescent staining of human colonic mucus was performed by the addition of 1 μg/mL of the Cy5-conjugated peptides (Green) with Dapi (1:100) (Blue) and Phalloidin-RRX (1:1000) (Red). Image acquisition was performed using a fluorescent confocal microscope (see Methods).

FIG. 32. BLAST alignment performed between MUB40-1 sequence (SEQ ID NO: 62) and corresponding sequences in several species to identify MUB40-1 variants (SEQ ID NO: 69 to SEQ ID NO: 83). MUB₄₀₋₁ sequence is in bold. Conserved patterns P8, P9 and P10, as detailed herein, are indicated and highlighted in light and/or dark gray. Perfect match over all compared sequences are identified with an asterisk. Good matches are identified with a double dot or a dot.

EXAMPLES

A. Materials and Methods

Chemical Synthesis

MUB₇₀ Synthesis. Synthesis was carried out on an ABI 433 synthesizer (Applied Biosystems, Foster City, Calif., USA) equipped with a conductivity flow cell to monitor Fmoc deprotection. PS-PHB-Phe Fmoc resin (capacity 0.52 mmol/g) was purchased from Rapp Polymere GmbH (Tübingen, Germany). Dmb- and pseudoproline (oxazolidine) dipeptides were purchased from Merck-Novabiochem (Darmstadt, Germany). Standard Fmoc amino acids were obtained from Applied Biosystems, and side-protected as followed: tBu for aspartic acid, glutamic acid, serine, threonine and tyrosine, trityl for cysteine, histidine, Boc for lysine, and 2,2,4,6,7-pentamethyl-dihydrobenzofuran-5-sulfonyl for arginine. Fmoc-amino acids and pseudoproline dipeptides were activated with HATU/DIPEA and single coupled with a eightfold molar excess with regard to the resin. Both coupling reagents, as well as N-methyl pyrrolidone (NMP), were purchased from Applied Biosystems. Piperidine was purchased from Sigma-Aldrich (St Louis, Mo., USA). (Synthesis yield 85.4%). Synthesized peptide was collected through classical resin cleavage and HPLC detection techniques. Purification was achieved using a three-step purification method on the dimeric form of MUB₇₀. Biotin and Cy5 conjugations are described herein.

Any synthesized peptide mass was calculated using electrospray ionization mass spectrometry.

MUB40-Peptides Chemical Synthesis:

The synthesis strategy used for synthesizing the MUB70 fragment has also been used for synthesizing the overlapping four shorter Mub40 sequences (41). Taking into account the necessity to introduce secondary amino acid surrogates to obtain MUB70, the inventors have preserved in the MUB40 operating sequences both Dmb and pseudoproline dipeptides incorporation in the positions which have been shown to be beneficial (see FIG. 17). As a result, lowering of aggregation propensity and aspartimide formation produced the MUB40 peptides with a satisfactory yield.

Synthesis and cleavage. The synthesis were carried out on an ABI 433 synthesizer (Applied Biosystems, Foster City, Calif.) equipped with a conductivity flow cell to monitor Fmoc deprotection, from a polystyrene AM-RAM resin (capacity 0.41 mmol/g, Rapp Polymere GmbH). Fmoc amino acids, Dmb, and pseudoproline dipeptides were activated with HCTU (2-(6° Chloro-1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium hexafluorophosphate)/DIPEA (N,N-diisopropylethylamine) and single-coupled with an eight-fold molar excess regarding the resin. Fmoc-Asp(OtBu)-(Dmb)Gly-OH dipeptides and pseudoproline (oxazolidine) dipeptides were purchased from Merck-Novabiochem. Both coupling reagents, N-methyl pyrrolidone (NMP) and standard Fmoc amino adds were obtained from Applied Biosystems. Fmoc amino adds were side-protected as followed: tBu for aspartic acid, glutamic acid, serine, threonine and tyrosine, trityl for cysteine, histidine, Boc for lysine, and 2,2,4,6,7-pentamethyl-dihydrobenzofuran-5-sulfonyl (Pbf) for arginine. Piperidine was purchased from Sigma-Aldrich (St Louis, Mo., USA).

N-terminal acetylation was achieved by treating the peptide resin at the end of the synthesis with acetic anhydride for 30 minutes. As a result, the Mub40 peptides were N-terminal amide and C-terminal acetylated.

Cleavage from the solid support and deprotection of the amino acid side chains were accomplished in one step by treatment with 92.5:2.5:2.5:2.5 mixture of TFA (Applied Biosystems), ethanedithiol, triisopropylsilane (Sigma-Aldrich) and water for 3 h at room temperature. After filtration of the resin, the cleavage mixture was poured into ice-cold diethyl ether. The precipitate was recovered by centrifugation, washed three times, dried, resuspended in a mixture of water and acetonitrile and freeze dried.

HPLC analysis. Analysis of crude mixtures and purity control of the final peptides were performed by RP-HPLC on an Agilent (Santa Clara, Calif., USA) 1100 Series liquid chromatograph and monitored with a photodiode array detector by absorbance at 230 nm, according to the following methods. A linear gradient from 15% to 40% of acetonitrile in aqueous solvent A (50 mM ammonium acetate, pH 6.5) over 20 min was applied at a 0.35 ml/min flow rate on a Symmetry 300 C18 3.5 μm 2.1×100 mm column (Waters, Manchester, UK).

Purification. The free sulfhydryl crude peptides Mub40-1, 2 & 3 were solubilized at a final concentration of 20 mg/ml in a mixture of solvent A and acetonitrile, 8:2 v/v. Crude Mub40-4 was solubilized at the same concentration in water with aqueous ammoniac (pH8) and 10 equivalent of DTT (1,4-Dithio-DL-threitol). Those materials were purified by RP-MPLC (AP-100/200 flash, Armen Instrument, Saint Ave, France) on a preparative column (26×313 mm) packed with 100 Å20 μm C18 Nucleoprep packing (Macherey & Nagel GmbH & Co, Düren, Germany), by applying a linear gradient of 15-70% solvent B (mixture of acetonitrile and solvent A, 8:2 v/v) in solvent A over 60 min at a 20 ml/min flow rate. The purification was monitored at 214 nm (UV detector K2501, Knauer, Berlin, Germany). The suitable fractions were pooled and freeze dried. The overall isolated yields (from 20% to 30%) were in concordance with the observed synthesis yields deducted from the crude's HPLC analysis.

Conjugation. The Cy5 conjugation was operated in a 0.1 M Phosphate buffer pH=6, using 1.2 equivalent of the correspondent maleimide derivative (InvitroGen) in the presence of 1.5 equivalent of TCEP (Tris(2-carboxyethyl)phosphine) per mole of cysteine residue. The labeled peptides were purified after 30 minutes of coupling reaction by RP-HPLC on a nucleosil 5 μm C18 300 Å semi-preparative column, using a linear gradient of 15-40% acetonitrile in solvent A over 20 min at a 6 ml/min flow rate. The purity was checked according the former described HPLC analytical method. The exact concentration was determined by quantitative amino acid analysis (Hitachi, L-8800 analyzer), giving from 50% to 60% conjugation yield.

Electrospray ionisation mass spectrometry. Mass spectrometry was carried out on a quadrupole-TOF Micro mass spectrometer (Waters) equipped with a Z-spray API source and calibrated with a phosphoric acid calibration solution. Capillary, sample cone and extraction cone voltages were set at 3 kV, 40V and 10V. respectively. Source and desolvation temperatures were set at 80 and 250° C., respectively. Data were acquired by scanning over the m/z range 150-2000 at a scan rate of 1 s and an interscan delay of 0.1 s. Peptides were dissolved in a mixture of water/methanol/acetic acid 49.5/49.5/1 v/v/v at a concentration of 1 μg/μl and analysed in positive-ion mode by infusion at a flow rate of 5 μl/min. About fifty spectra were combined and the resultant raw multicharged spectra were processed using the MaxEnt1 deconvolution algorithm embedded in the Masslynx software. Given the deconvolution process of MaxEnt1, applied to the charged molecules (the Cy5 moiety is positively charged), final characterization was consistent with the expected masses: Cy5-labeled MUB40-1: experimental 5549,740—expected 5550,115; Cy5-labeled MUB40-2: experimental 5447,472—expected 5447,933; Cy5-labeled MUB40-3: experimental 5588,273—expected 5589,170; Cy5-labeled MUB40-4: experimental 5501,778—expected 5502,093. Characterization data is provided in FIGS. 18, 19, 20 and 21.

Biochemical Characterization and Biological Properties

Analytical Gel filtration. 25 μg of biot-MUB₇₀ was applied with a flow rate of 0.2 ml/min to a Superdex™ 5/150 column (Tricorn™) (GE Healthcare, Uppsala, Sweden) that was equilibrated with 5 CV of gel filtration buffer (25 mM TRIS, 150 mM NaCl, pH 7.5) at 4° C. before use. Standard proteins from the gel filtration calibration kit (ferritin, aldolase, ovalbumin, ribonuclease A, aprotinin; GE Healthcare, Uppsala, Sweden) were used for calibration. As control biot-MUB₇₀ was visualized on 10% SDS-PAGE gel stained by Coomassie.

Colonic tissue collection. Ex vivo human colon samples were obtained from Dr. E. Labruyère (Institut Pasteur) and tissue processing was performed as described previously [27] and stored in serum free RMPI media (surgical procedure is described herein). Human mucinous carcinoma formamide fixed samples were obtained from Dr. T. Lazure (Hôpitaux Universitaires Paris-Sud, Kremlin-Bicêtre) and Pr. I. Sobhani (Hôpital Henri Mondor, Créteil). Rabbit colon and ileum samples were collected on naïve New Zealand white rabbits weighting 2.5-3 kg and fixed in PFA 3%. Same procedure was applied on intestine samples collected on guinea pigs (Charles River) and C57/B6 mice (Janvier).

Cell culture. Hela cells were grown in DMEM medium supplemental with 10% FCS. HT-29 MTX colonic epithelial cells [28] were grown to confluency in 24-well tissue culture plates in RPMI medium supplemented with 10% FCS and 1% essential amino acids. Mucus production in HT-29 MTX cells was observed after 21 days. Cell viability was determined by staining with Sytox Green (Invitrogen) as described by the manufacturer. Sytox Green only penetrates into and stains the DNA of non-viable cells. As a positive control, cells were killed by incubation in 3% PFA for 15 min (data not shown). Fluorescence was measured using a FACS flow cytometer (BD systems) recording at least 10,000 events. Data were analysed with CellQuest Pro software (BD Biosciences), and expressed as percentage survival.

Antibodies and MUB₇₀ probes. For immunofluorescence assay mouse α-MUC2 pAbs (Santa Cruz sc-15334) was diluted 1:1000 and FITC-conjugated rabbit anti-mouse was diluted 1:2000. Host cells were detected with DAPI (nuclei, red) or using Phalloidin-Rhodamine red X (RRX)-conjugated donkey anti-mouse antibodies (Jackson Immunoresearch Antibodies) as an actin marker (stained red); both were used at a final dilution of 1:1000. Cy5-MUB₇₀ (1 mg/mL solution) was diluted 1:1000.

For dot blot assay, goat α-MUC2 pAbs (sc-13312, Santa Cruz), mouse α-MUC5ac (Abcam), mouse α-MUC5b mAbs (Abcam), mouse α-MUC6 mAbs (sc-33668, Santa Cruz), mouse α-lactoferrin mAbs (sc-52048, Santa Cruz) and rabbit α-FCGBP pAbs (Sigma-Aldrich) antibodies were used at a 1:100 dilution. Corresponding HRP-Conjugated antibodies were used at a 1:1000 dilution. For staining living HT-29 MTX cells and on human colon ex vivo model, Cy5-MUB₇₀ was incubated (1 μg/mL) in a serum starved culture medium (DMEM and RPMI respectively) for two hours at 37° C. prior observation.

Mucus collection. In order to perform a pulldown assay, soluble human colonic mucus extracts were initially obtained from HT-29 MTX cell secretion product (as described in [29]. Briefly, mucus was collected using cold PBS. After sonication and centrifugation (14000 rpm, 30 min), the supernatant containing the soluble mucus fraction was lyophilized (Labologic, Freeze Dryer). Eight independent batches of human mucus were processed.

Deglycosylation, desialylation. Mucus collected from HT-29 MTX (see above) was chemically deglycosylated using a GlycoProfile IV chemical deglycosylation kit (Sigma-Aldrich). Each treatment was performed on two independent samples. 4 mg of lyophilized mucus were processed per batch as recommended by the manufacturer. Desialylation and desulfatation were performed on 2 mg lyophilized mucus batches by adding respectively 1 mU/mL of C. perfringens neuraminidase (Neu1) (Sigma-Aldrich) in PBS 50 mM pH=6 and A. aerogenes sulfatase in TrisHCl 50 mM pH=7.25, KCl 100 mM and 10 mM MgCl₂. Reaction mixtures were incubated 2 h at 37° C.

Pulldown assay. Pulldown assays were performed in the presence of 600 μg biot-MUB₇₀ bound to 500 μL Avidin-agarose beads (Thermo Scientific) in a Phosphate Buffer pH=8 buffer for 1 h at 4° C. After 3 washes, 10 mg soluble human colonic mucus extract were incubated with the loaded beads for 2 h at 4° C. After 3 washes, beads were boiled in the presence of 1× Laemli buffer. As a negative control, Avidin-agarose beads were loaded with 15 μg biotin (Sigma-Aldrich) and processed using the same procedure. Experiments were performed on two independent occasions.

Dot blot assay. Soluble mucus components used in pulldown assays (input and output) were transferred to nitrocellulose membranes (Invitrogen), which were blocked in PBS/5% milk and further incubated with the primary antibodies diluted in PBS/1% milk/0.01% Tween20 (Sigma-Aldrich) overnight. Membranes were washed in PBS three times, then incubated with secondary antibodies for 1 hr before washing. Antibody binding was detected with chemiluminescence (ECL kit, GE Healthcare).

Tissue immunostaining. Following PFA 4% or Carnoy fixation, as indicated, samples were washed in PBS, incubated at 4° C. in PBS containing 12% sucrose for 90 min, then in PBS with 18% sucrose overnight, and frozen in OCT (Sakura) on dry ice. 7 μm sections were obtained using a cryostat CM-3050 (Leica).

Fluorescence microscopy. Fluorescent labeled tissues and cells were observed using a widefield epifluorescent microscope (Zeiss Definite Focus), laser-scanning confocal microscope (Leica TCS SP5) or a two-photons confocal microscope (Zeiss LSM710), as indicated. Image analysis was performed using Axovision, ImageJ, Zen 2008 SP 1.1 (Zeiss) and Imaris softwares as indicated.

Cleavage from the resin. Cleavage from the solid support and deprotection of the amino acid side chains were accomplished in one step by treatment with 92.5:2.5:2.5:2.5 mixture of TFA (Applied Biosystems), ethanedithiol, triisopropylsilane (Sigma-Aldrich) and water for 3 h at room temperature. After filtration of the resin, the cleavage mixture was poured into ice-cold diethyl ether. The precipitate was recovered by centrifugation, washed three times, dried, resuspended in a mixture of aqueous acetic acid and acetonitrile and lyophilised. (cleavage yield 76%).

HPLC analysis. Analysis of crude mixtures and purity control of the final peptides were performed by RP-HPLC on an Agent (Santa Clara, Calif., USA) 1100 Series liquid chromatograph and monitored with a photodiode array detector by absorbance at 230 nm, according to both following methods a or b. A linear gradient (from a/30% to 40% or b/15% to 40%) of B (acetonitrile) in aqueous solvent A (a/0.08% aqueous TFA, pH 2 or b/50 mM ammonium acetate, pH 6.5) over 20 min was applied at a 0.35 ml/min flow rate on a Symmetry300 C18 3.5 μm 2.1×100 mm column (Waters, Manchester, UK). LC-MS data were obtained using a Waters Alliance 2695 system comprising a 2487 dual absorbance detector and coupled with a TOF-MS detector (Waters Q-TOF Micro) with the following eluents: A: water containing 0.05 formic acid and 0.04% TFA, B: solution of acetonitrile containing 0.025% formic acid. Data acquisition and process are described bellow.

Three-step purification. Solubilisation of quantitative amounts of crude peptides was achieved by mixing the lyophilised material in glacial acetic acid and rapidly diluting with water so that the final concentrations were 20 mg/ml of peptide in 20% aqueous acetic acid. This material (loading 150 mg per run) was directly purified by RP-MPLC (AP-100/200 flash, Armen Instrument, Saint Ave, France) on a preparative column (26×313 mm) packed with 100 Å20 μm C18 Nucleoprep packing (Macherey & Nagel GmbH & Co, Düren, Germany), by applying a linear gradient (0.5%/min) of 30-60% solvent B (mixture of acetonitrile and solvent A, 8:2 v/v) in solvent A (0.08% aqueous TFA) over 60 min at a 20 ml/min flow rate. Preserving acidic environment prevent dimerisation. The purification was monitored at 214 nm (UV detector K2501, Knauer, Berlin, Germany). Suitable fractions were pooled and lyophilised. (Yield 16.2%). This material was solubilised in water by adding a small amount of aqueous ammoniac in order to raise a pH of 7.5, with 2.5 equivalents of TCEP, then subjected to a second step of purification using a linear gradient (0.4%/min) of 15-40% solvent B (mixture of acetonitrile and solvent A, 8:2 v/v) in solvent A (50 mM ammonium acetate, pH6,5) over 60 min at a 20 ml/min flow rate. In this neutral pH conditions, dimerisation occurred during the run and was led to completion before lyophilisation of the suitable fractions. (Yield 49%). The resultant dimeric peptide enriched mixture was submitted to a third step of purification by applying the first step procedure in the same acidic conditions. The retention time of the dimeric form of the target peptide was shifted about four minutes as compared to the monomeric form and the associated truncated peptides. (Yield 39%) Overall isolated unlabeled peptide yield: 2% (to be compared with 25% observed yield from HPLC analysis).

Conjugation. Biotin and Cy5 conjugation were operated in water upon the dimeric form of the MUB peptide using the correspondent maleimide derivatives in the presence of 3 equivalents of TCEP per mole of cysteine residue. pH was adjusted to 8 with aqueous ammoniac solution. The biotinylated peptide was obtained after addition of 2 equivalents of maleimide-PEG2-biotin (Pierce, Rockford, Ill., USA). The cy5 labeling was achieved by addition of 1.2 equivalent of Cy5 Mono Maleimide (InvitroGen). Both conjugates were purified after 30 minutes of coupling reaction by RP-HPLC on a nucleosil 5 μm C18 300 Å semi-preparative column, using a linear gradient (0.75%/min) of 30-45% acetonitrile in 0.08% aqueous TFA over 20 min at a 6 ml/min flow rate. The purity was checked according the former described HPLC analytical method. The exact concentration of the purified conjugates was determined by quantitative Amino Acid Analysis; giving 69% and 20% conjugation yields for the biotinylated and the cy5-labeled products, respectively. Both constructs are resuspended in a 0.1 M Phosphate buffer pH=8, containing 0.15 M NaCl.

Electrospray ionisation mass spectrometry. Mass spectrometry was carried out on a quadrupole-TOF Micro mass spectrometer (Waters) equipped with a Z-spray API source and calibrated with a phosphoric acid calibration solution. Capillary, sample cone and extraction cone voltages were set at 3 kV, 40V and 10V, respectively. Source and desolvation temperatures were set at 80 and 250° C., respectively (raised to 120 and 400° C. in the higher flow rate conditions of LC). Data were acquired by scanning over the m/z range 150-2000 at a scan rate of 1 s and an interscan delay of 0.1 s. Lyophilised crude and purified products were dissolved in a mixture of water/methanol/acetic acid 49.5/49.5/1 v/v/v at a concentration of 1 μg/μl and analysed in positive-ion mode by infusion at a flow rate of 5 μl/min. Three hundred spectra were combined and the resultant raw multicharged spectra were processed using the MaxEnt 1 deconvolution algorithm embedded in the Masslynx software. LC/MS data were obtained by selecting and combining spectra of separate peaks and shoulders of the Total Ionic Current chromatograms. Final characterization was consistent with the expected mass: biotinylated MUB (biot-MUB₇₀): experimental 8755,374—expected 8755,468; Cy5-labeled MUB: experimental 9009,565—expected 9009,797.

Colon explants surgical collection. In summary, human colon explant preparation Segments of human colon (ascending, descending and sigmoid colon) were obtained from fully informed patients undergoing surgery for colon carcinoma and were analyzed anonymously. Patient written consent was obtained, according to the French bioethics law. None of the patients had undergone radiotherapy or chemotherapy. According to the pathologist's examination rules for the longitudinally bisected colon, a healthy segment of tissue which was distant from the tumour region and devoid of metastatic cells was removed. Tissues were processed according to the French Government guidelines for research on human tissues and the French Bioethics Act, with the authorization n° RBM 2009-50.

Two-photons microscopy. Two-photons microscopy imaging of live healthy human colonic segment was performed using a commercial laser-scanning microscope (LSM710, Meta, Zeiss, Germany). Tissue autofluorescence and Cy5-MUB₇₀ (1 μg·ml⁻¹) were detected using multiphoton excitation (MPE, red) and collagen was detected using second harmonic generation (SHG, green). All samples were imaged immediately following tissue dissection. Illumination of samples for both MPE and SHG was accomplished using a TI: sapphire femtosecond laser (140 fs, 90 Mhz) tunable from 690 to 1040 nm (Cameleon ultra I, Coherent, inc). Excitation was performed using an output wavelength of 820 nm. Beam was focused onto samples using a ZEISS Plan-apochromat 20× objective, 1-NA water-immersion (Axial resolution are; Rxy=0.64 μm, Rz=5 μm). Both MPE and SHG were collected in a backscattering geometry using the nondescanned detection. Detection bandwidth of MPE and SHG signals were respectively 570-610 nm (pseudocolored red) and 300-480 (pseudocolored green). Two dimensional (x,y plane) images (512×512 pixels per frame, each image was acquired in 6.71 seconds) were acquired from various depths (z increment of 3 μm). Acquisitions were performed with Zen 2008 SP 1.1 software acquisition package developed by ZEISS. Imaris software (http://www.bitplane.com) was used to prepare images.

Production of MUB70-SNAP in S2 Insect Cells

MUB70 gene synthetic synthesis. The synthesis of the gene corresponding to MUB70 was performed by Genecust. This sequence include the EcorV/SmaI restriction sites. The gene sequence is:

(SEQ ID NO: 66) tcgcgaggatccggtgatatcgttcacgttcaatacattgatggt gaaactgaccagatgctgcgtcaggatgatttggacggctacacg gatgaaacgattccttacagcacggctgaaggcatcaagaagttt gaaggcgacggttatgaactgttcaaggacaacttcccagctggt gagaagttcgataacgatgacaccaacgatcaattctacacggta atcttcaagcaccatcgtggcccgggagggcccaagctt MUB70 Gene Cloning into pDeSNAPUniv Shuttle Vector

The MUB70 DNA fragment and the pDeSNAPUniv shuttle vector (described in patent application WO2012/076715) were digested using the XmaI and EcorV dephosphorylated restriction enzymes prior cloning into E. coli DH5alpha host bacteria. The resulting sequenced construct was further digested using the BglII and AgeI restriction enzyme for a subsequent cloning in the pMT/BIP/V5-HisA plasmid digested with the same enzymes. The resulting construct was transformed in SURE2 bacteria (Stratagene) and left 5 days at room temperature. Transformed bacteria were grown in LB medium in the presence of Ampicillin (100 g/mL) at 28° C.

S2 Insect Cell Transformation

S2 insect cells (Drosophila) were co-transfected by the resulting pMT/BIP/SnapUniv-MUB70 plasmid and pCOBlast (encoding for a Blasticidine resistance gene) using a Qiagen Effectène kit. A stable cell line was further obtained by a series of successive passages (at least 7, twice a week) in the presence of 10 g/mL Blasticidine. As a production control test, 5 μM of Cadium chloride was added for 10 days in the S2 cell culture medium. The presence of MUB70-SNAP in the supernatant was analysed by Western blot using an anti-SNAP antibody.

MUB70-SNAP Production in S2 Cells

The transfect S2 cells were grown in a Insect Xpress liquid media (1 L) containing g/mL Blasticidine. When the culture reached 9.106 cells/mL The protein production induction was activated by the addition of 5 μM CdCl2 for 11 days. The supernatant was harvested by centrifugation (6000 rpm, 30 min) and concentrated 10 times on a Vivaflow 200 system and further dialysed in PBS containing 0.5 M NaCl and 5 mM Imidazole. The first affinity purification step was performed on a Talon beads. The elution step was performed in the presence of 200 mM Imadazole. The second purification step was performed by gel filtration on a HiLoad 16/60 Superdex 75 column (GE Healthcare) equilibrated with a 20 mM Tris pH 8 buffer containing 200 mM NaCl. The flowrate was 1 mL/min. A series of two successive runs were performed allowing a purity >95% to be reach

B. Results and Discussion

Identification of MUB₇₀ in L. reuteri AF120104 protein sequence. MUB₇₀ was initially identified in Mucin Binding Proteins (MucBP), associated with the well-characterized Mucin Binding Domains (MucBD, PFAM 06458). However, this domain was described as being present in some but not all proteins of this family [26], reflecting the diversity of MucBP sequences and sizes (FIG. 1A). Shorter MucBP do not contain MUB₇₀ (i.e. L. plantarum Ip-1229 sequence [30], (FIG. 1A). The MUB₇₀ sequence could not be associated with a PFAM known homologous domain, thus its function remained unknown [26]. The sequence was named MUB₇₀ as its minimum conserved sequence among Lactobacillus strains is 70 amino acids. MUB₇₀ has been observed to be repeated from 1 to 18 times in different L. reuteri cell-surface proteins [26]. In L. Reuteri AF120104 cell-surface precursor protein, MUB₇₀ homologous sequences are repeated 13 times (SEQ ID NO: 4 to SEQ ID NO: 15), as described by Roos and co-workers [25] (FIG. 1B). Sequence comparison was performed between these sequences showing that repeats #7 and #9 are identical and are the most conserved sequences among others (Table 1). MUB₇₀ repeat #7 sequence possesses 23% identity with AF120104 homologous proteins MUB₇₀ domains in other lactobacillus strains (L. gasseri, L. johnsonii, L. fermentum and L. delbrueckii) (FIG. 1C). This peptide (MUB₇₀ repeat #7) was selected as a model for chemical synthesis.

Synthesis of Cy5-MUB₇₀ and biot-MUB₇₀. Despite considerable evolution in the field, straight chemical synthesis of long peptide chains remains a difficult task. Considering Solid Phase Peptide Synthesis, initiated by Merrifield [31], most of the deprotection and coupling difficulties are related to inter or intra-molecular hydrogen bonds occurring over the synthesis. N-alkylated amino-acids such as Dmb/Hmb [32] or pseudoproline [33] have been more recently developed to overcome the aggregation propensity of the protected peptide chain anchored on the resin. Here, the presence of hydroxyl amino acids into MUB₇₀ sequence has provided the opportunity to introduce several properly spaced pseudoproline dipeptides. A single cystein was incorporated at the N-terminus to allow N-terminal specific labeling (FIG. 5). Using a classical Fmoc/tBu methodology (Strategy 2, FIG. 5) [34], a first synthesis at a 100 μmolar scale was achieved, from a polystyrene-based resin. The peptide-resin was processed with a TFA cleavage solution and the resulting crude product (weight yield 66%) was analyzed by HPLC and LC-MS in acid conditions. A 0.5%/min gradient of acetonitrile in acidic buffer was applied on a RP C18 Symmetry column (Waters) and the low pH of the injected sample therefore preserved to prevent oxidation of the cystein residue. In these conditions, the target peptide was detected as a major peak (around 8% by area integration) in a quite complex chromatogram (FIG. 6). Moreover, MS analysis of this major peak revealed the presence of a complex mixture of similar peptides with a mass deviation of −18 or +67, reflecting the presence of aspartimide and piperidine by-products in a mostly significant amount. Aspartimide formation [35] and subsequent base-catalyzed ring-opening during Fmoc-SPPS has been described to be strongly dependent of the previous coupled amino-acid [36] in relation with the global mixing time of the Asp-containing peptide resin in the FMOC deprotection solution [37]. Indeed MUB₇₀ sequence accumulates eight highly sensitive occurrences (3 Asp-Gly, 2 Asp-Asn, 2 Asp-Asp, 1 Asp-Thr), among which Asp-Gly sequences are particularly prone to aspartimide formation. A systematic protection of each glycine amide moiety occurring before an Asp derivative coupling was achieved by coupling Fmoc-Asp(OtBu)-(Dmb)Gly-OH dipeptides (Strategy 2, FIG. 5), namely in position 29, 50 and 63 in reference to the C-terminus [38]. As a result the disaggregation of the peptide chain was improved and accordingly the deprotection and coupling efficiency (FIG. S1). The resulting resin was processed and the crude was analyzed by LC-MS according to the same protocol. Although the weight yields calculated from the crude products were similar (65%) the target peptide peak area integration was increased from 8% to 25% (FIG. S2B).

A first RP-MPLC purification protocol was applied in acidic environment (pH=2) in order to maintain the peptide in its reduced form. The remaining aspartimide and piperidine side products (FIG. 6C) were shown to be well separated when analyzed by RP-HPLC in neutral conditions, using 50 mM ammonium acetate (pH6.5) as aqueous buffer (data not shown). Despite the presence of 2.5 equivalents of TCEP as reductive agent into the loaded mixture, scaling up this protocol through a second RP-M PLC purification step revealed the high propensity of this material to dimerize in acetonitrile containing solution. Moreover, oxidation of the sulfhydryl moiety occurred along the run and was led to completion before lyophilization. RP analysis at pH=2 of the resulting partially purified material showed a significant shift between both dimer and monomer-associated truncated peptides retention times (FIG. 6D). Consequently a last RP-MPLC purification step was achieved by repeating the former protocol to yield the MUB dimeric form with above 90% purity (FIG. 2A).

To summarize, improvement of the synthesis by the incorporation of Dmb and pseudoproline dipeptides, followed by a three steps purification process were combined to isolate the target peptide (FIG. 6E) as covalent dimer with an overall weight yield of 2%. Monomer recovery and simultaneous conjugation of biotin or fluorophore via the maleimide derivatives are described in Methods.

Biochemical properties of MUB₇₀. MUB₇₀ is predicted to be a negatively charged peptide at a pH higher than 4 (net charge at pH=7 is −12.9), (FIG. 7C) even though the surface charge of MUB₇₀ is still unknown. No specific hydrophobic domain was predicted through a Kyte-Doolittle analysis of MUB₇₀ (FIG. 7D). This result is consistent with its high solubility in a phosphate buffer at pH=8 (see Methods). The theoretical molecular weight (MW) of a biotinylated MUB₇₀ (biot-MUB₇₀) is 8.8 kDa. However when migrating on a SDS-PAGE gel, the apparent MW is around 28 kDa and this result is independent from the pH, which seems to indicate a stable oligomerization of biot-MUB₇₀ (FIG. 2B). This observation was confirmed with the fluorescent Cy5-MUB₇₀ compound (data not shown). In order to confirm the predicted trimeric organization of MUB₇₀, an analytical gel filtration was performed on biot-MUB₇₀ in order to determine its quaternary structure. The elution profile was recorded at 280 nm. At 0.1 and 1 mg/ml, biot-MUB₇₀ gave a single peak at an elution volume of 2.1 ml (FIG. 2C and FIGS. 7A and 7B). The molecular mass was determined to be 27.9 kDa, proposing that biot-MUB₇₀, with a theoretical mass of 8.8 kDa, exists as trimer in phosphate buffer.

Cell toxicity of MUB₇₀. As Cy5-MUB₇₀ was envisaged to be used on living cells and organs, its cell-toxicity has been evaluated. This probe was incubated on differentiated HT-29 MTX and on Hela cells as cell viability was assessed using a Sytox Green assay (see Methods). Incubating MUB₇₀ (1 μg/mL) for up to 10 h in a serum starved media do not affect significantly cell viability (Student test, NS, p>0.05, n=3) (FIG. 8A). This result was consistent with the hydrophilic property of MUB₇₀ (FIG. 7D) which does not allow cell penetration. The absence of intracellular fluorescent signal upon exposure of different living cell types (phagocytic and non-phagocytic cells) exposed to Cy5-MUB₇₀ (1 μg/mL in a serum free media) (i.e. human epithelial cells, human myeloid cells, human ES cells, mouse dendritic cells, data not shown) was also confirmed.

Specific staining of human, rabbit and guinea pig colonic mucus Using Cy5-MUB₇₀. Cy5-MUB₇₀ was incubated on living differentiated HT-29 MTX human epithelial colonic cells, which have the property to constitutively produce a mucus layer after differentiation (see Methods). As observed using a live epifluorescent microscope, Cy5-MUB₇₀ was binding the mucus layer at the surface of the cells. A Z-projection observation allowed the visualization of fluorescent mucus patches, typical of mucus aggregates produced by differentiated HT-29 MTX cells [28], as cells remained unstained (FIG. 3A). This result demonstrates that MUB₇₀ is a new Mucus Binding Domain (MUcBD). This observation was confirmed by incubating Cy5-MUB₇₀ on human colon explants. As shown in FIG. 3B, the mucus layer, observed using a two-photons microscope, is stained heterogeneously on the whole width (estimated around 1000 μm) as the epithelium and lamina propria remain unstained. Proportion of mucus stained by Cy5-MUB₇₀ might depend on Cy5-MUB₇₀ concentration and on the thickness of the mucus layer, as thinner layers could be stained until epithelium surface (FIG. 8C). Staining kinetic analysis indicates that Cy5-MUB₇₀ is widely detected after 90 min onto a 1 mm thick mucus layer (FIG. 4D).

Different animal models were used to confirm this result: rabbit, guinea pig and mouse colon were tested. Interestingly colonic mucus staining using Cy5-MUB₇₀ was confirmed on rabbit and guinea pig models (FIG. 11A and FIG. 11B). However, mouse colonic mucus was not stained applying the same procedure (FIG. 11C), which indicates major differences in its composition compared to human. The specific colonic mucus binding property of Cy5-MUB₇₀ was confirmed on the rabbit model, as negative results were obtained on ileal mucus samples (FIG. 8D). These results rule out the possibility of aspecific trapping of Cy5-MUB₇₀ in mucus layers and as a control, Cy5 fluorophore does not have the property to bind human mucus (FIG. 10A). As a conclusion, these results suggest that Cy5-MUB₇₀ interacts with a colonic mucus secreted specific component present in human, rabbit and guinea pig but not in mouse.

Biot-MUB₇₀ binds specifically to glycosylated Muc2 from colonic mucus. In order to identify a MUB₇₀ ligand present in the soluble extracts of human colonic mucus, biot-MUB₇₀, a biotinylated form of MUB₇₀, was synthesized (see Methods) in order to perform pulldown assays. Biot-MUB₇₀ was incubated with avidin beads and further with human colonic mucus extracts (produced in vitro from differentiated HT-29 MTX cells, see Methods). Biotin only was used as a negative control. Following initial attempts aimed at separating eluted proteins on SDS-page gel, Coomassie staining did not allow the identification of any specific protein (data not shown). A dot blot assay was then performed, focusing on secreted mucins, which are the major components of colonic mucus. Muc2 was immunodectected in the eluted fraction, and not in the negative control, and Muc5ac, Muc5b or Muc6, all detected in the input were absent from the eluted fraction (FIG. 4A). This result was confirmed by immunofluorescence colocalization detection of Muc2 and Cy5-MUB₇₀ on human colon mucus purified from ex vivo samples (FIG. 4B) and fixed purified human mucus and rabbit colon samples (FIGS. 9A and 9B). Processing a chemical deglycosylation step on the soluble mucus extract (see Methods) prior to pulldown assay abolished the interaction between Muc2 and biot-MUB₇₀ (FIG. 4A). It was specifically demonstrated that desulfatation (glycosylsulfatase) but not desialylation (neuramidase) lead to a loss of this interaction (FIG. 4A), highlighting the role of sulfate groups found specifically on human colonic mucus [12] in the binding of MUB₇₀. This result could explain the differential staining observed on rabbit ileal and colonic mucus (see above and FIG. 8B) as Muc2—expressed and secreted in both organs—possesses differential glycosylation patterns [9] [12]. As a conclusion, MUB₇₀ binds sulfated Muc2 oligosaccharides in colonic mucus thus exploiting its specific glycosylation profile. As a control, considering that Muc2 has been recently shown to bind covalently Fca-binding-protein (FCGBP) [39], the role of this partner of Muc2 in the association with MUB₇₀ was analyzed. As FCGBP binds aspecifically to the biotin-conjugated avidin beads moiety (FIG. 10B), it was not possible to directly exclude a role of this protein in the Muc2/MUB₇₀ interaction. However, indirectly, after deglycosylation, as an abolishment of the Muc2/MUB₇₀ interaction was observed (see above, FIG. 4A) it was not the case of FCGBP binding to biotin (FIG. 8B). In addition, the colon-versus-ileum specificity of mucus MUB₇₀ binding observed in rabbit samples (FIG. 8B) excludes any role of FCGBP. These results suggest no specific role of FCGBP in the Muc2/MUB₇₀ interaction.

Cy5-MUB70 is a new specific marker for colonic mucinous carcinomas. As colonic mucinous carcinomas are characterized by abnormal overproduction of Muc2 in the colon mucosa (40), the inventors have hypothesized that Cy5-MUB70 could be used as a novel fluorescent marker for the diagnosis of this pathology. They have demonstrated, on five different samples collected from patients diagnosed with colonic mucinous carcinomas, that a specific staining was observed within the mucus accumulation areas (a representative sample is shown in FIG. 24B). As shown previously on a healthy colon (FIG. 3B), the luminal mucus secreted fraction is detected by Cy5-MUB₇₀ (FIG. 24A, top panel). As a control, no mucosal staining was observed in the colonic mucosa in healthy colon tissues originating from the same patients (FIG. 24A, lower panel). Interestingly, the inventors have shown that goblet cells are not recognized by Cy5-MUB₇₀. This observation might be the consequence of a higher level of mucus compaction, resulting in a lower accessibility for MUB₇₀ to bind Muc2. In colonic mucinous carcinomas (FIG. 24B), the fluorescent signal observed with Cy5-MUB70 (red) colocalizes with the presence of Muc2 (green) in the pathologic extensive mucus accumulation observed within the colonic mucosa and associated with tumor cells. Cy5-MUB₇₀ has been validated as a potent innovative diagnostic tool for colonic mucinous carcinoma detection and might be optimized with alternative markers (e.g. biotin) for practical clinical applications.

C. Conclusion

As a summary of the experiments described here-above, the synthesized L. reuteri MUBAD or MUB₇₀ is a new Mucus Binding Domain (MUcBD) which possesses oligomerisation properties which might contribute to the anchoring of these commensal bacteria in the colonic mucus layer. Chemically synthesized MUB₇₀ is a novel specific colonic mucus marker interacting with the sulfated moiety of Muc2 oligosaccharides, known as the main component of this epithelium surface protective layer. MUB₇₀ trimerisation property is believed to contribute to its interaction with Muc2 found in human, rabbit and guinea pig colonic mucus, not in mouse model. Conjugating MUB₇₀ with a fluorescent dye (i.e. Cy5) enables the provision of a new generation physiological probe allowing direct observation of colonic mucus in ex vivo and in vivo live imaging approaches, beyond classical immunofluorescence techniques. Furthermore, as mucins (including Muc2) expression and glycosylation modifications are frequently observed in mucinous carcinomas and IBD, targeting Muc2 with MUB₇₀ provides promising innovative approaches to develop new diagnostic tools.

The inventors have further synthesized shorter probes identified as MUB₄₀ probes herein, displaying the same properties than the MUB₇₀ probe. In particular, the MUB₄₀-Cy5#1 probe has proven to be a functional human mucus-binding peptide, additionally possessing globlet-cells binding properties in comparison with MUB₇₀-Cy5. This development exemplifies the pertinence of small probes encompassing the sequence(s) disclosed herein for the purpose of the invention.

The invention provides a solution for imaging living cells and organs, which requires innovative specific, efficient and well-tolerated fluorescent probes targeting cellular components and provides tools allowing to perform dynamic analysis of cell(s) and tissue(s) adaptation to environmental cues.

According to a particular embodiment of the invention, a novel non-toxic fluorescent marker of 70 amino acid peptide of unknown function frequently associated to MUB domains, named MUB₇₀, allowing specific fluorescent staining of human colonic mucus was identified, characterized and synthesized. In humans, the colonic mucus layer is on the average 500 μm thick and composed of different secreted gel-forming mucins (Muc2, Muc5ac, Muc5b, Muc6). Fluorescent peptide markers of 40 amino acids, named MUB₄₀ were also identified, characterized and synthesized. Muc2 is the most abundant secreted mucin forming the backbone of this cell surface protective layer. The synthesized peptide is highly conserved among Lactobacillus strains. Its chemical synthesis was achieved using the human commensal bacterium L. reuteri AF120104 protein as a template.

The synthesized Cy5-MUB₇₀ conjugated probe specifically stained colonic mucus, on fixed human, rabbit and guinea pig tissues, but not on murine tissues, indicating that the later shows significant difference in the composition of its colonic mucus. It was also shown that this probe also stained the mucus produced by cultured human colonic cells (HT29-MTX) and by human colonic tissue explants. As demonstrated using a biotinylated derivative of MUB₇₀, this peptide specifically binds to the glycoprotein Muc2, through its glycosylated moiety.

Hence Cy5-MUB₇₀ and Cy5-MUB₄₀ series are novel, specific fluorescent markers for mammalian colonic mucus that can be used for live imaging analysis and as marker for diagnostic and prognosis of mucinous carcinomas and IBD.

The chemical synthesis of fluorescent conjugated Cy5-MUB₇₀ and Cy5-MUB₄₀ series markers allowed the construction of a new generation of specific markers of mucus, especially colonic mucus, in particular carcinoma(s) colonic mucus, that might be used as a probes for live experimental imaging of the colon. In addition, further developments are anticipated in IBD and mucinous carcinomas to envision more accurate diagnostic and prognostic tools.

The inventors have shown, interestingly, that MUB70 is not toxic for living cells as it has no cell penetration property, allowing its specific localization in the mucus layer located on the epithelium surface. They also have proven the efficiency of the probes of the invention for investigating the colonic mucinous carcinoma. Muc2 expression is up-regulated in mucinous carcinomas affecting various organs, including the lung, the stomach, the breast, the prostate, and the bile ducts. Hence, targeting Muc2 with MUB₇₀, as observed on human colonic mucinous carcinomas, is anticipated to provide promising innovative approaches to develop new prognosis and diagnostic tools on various mucinous carcinomas.

The invention has also proven to be useful for the monitoring of neutrophile degranulation events, in particular by using MUB₇₀ and/or MUB₄₀ polypeptides or polypeptides sharing identity with MUB₇₀ and/or MUB₄₀ polypeptides, or fragments thereof, for labelling neutrophile granule(s). As illustrated in FIG. 31, the inventors have demonstrated the efficiency of all synthesized MUB₇₀ and MUB₄₀ polypeptides to this end: in the experiment corresponding to FIG. 31, and although a brighter signal was obtained with Cy5-MUB40-1 and Cy5-MUB40-4 probes, PMN granules were found to be efficiently stained on fixed cells with Cy5-MUB40-1, Cy5-MUB40-2, Cy5-MUB40-3 Cy5-MUB40-4, as compared to staining obtained with Cy5-MUB70.

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The invention claimed is:
 1. A polypeptide consisting of: (a) SEQ ID NO: 3 or (b) a fragment of SEQ ID NO: 3 , wherein said fragment has a length of at least 20 contiguous amino acid residues; wherein the polypeptide is coupled to a label or the polypeptide has an additional cysteine residue at the N-terminus.
 2. The polypeptide according to claim 1, wherein the polypeptide is coupled to a fluorophore or biotin.
 3. The polypeptide according to claim 1, wherein the polypeptide consists of SEQ ID NO: 3 or the fragment of SEQ ID NO: 3 consisting of SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, or SEQ ID NO:
 61. 4. The polypeptide according to claim 1, wherein the polypeptide consists of (a) SEQ ID NO: 3 or the fragment of SEQ ID NO: 3 consisting of SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, or SEQ ID NO: 61 and (b) a label.
 5. The polypeptide according to claim 4, wherein the label is a fluorophore or biotin.
 6. The polypeptide according to claim 1, wherein the polypeptide consists of (a) SEQ ID NO: 3 or the fragment of SEQ ID NO: 3 consisting of SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, or SEQ ID NO: 61 and (b) an additional cysteine residue at the N-terminus.
 7. A composition comprising a polypeptide according to claim 1 and a pharmaceutically acceptable excipient.
 8. A method, comprising staining living cell(s) or tissue(s) in in vitro experiments using a polypeptide according to claim 1 as a probe or marker.
 9. A method, comprising staining Muc2 protein(s) contained in mucus layer(s) using a polypeptide according to claim 1 as a probe or marker.
 10. A method, comprising a. detecting in vitro interaction with human colonic mucus in the adhesive mucus layer of colonic tissue sample using the polypeptide of claim 1 as a physiological labelled probe, or b. detecting in vitro mucus production or mucus composition in human colon, by contacting the polypeptide of claim 1 with a sample of colonic tissue comprising adhesive mucus layer and goblet cells.
 11. The method of claim 8, wherein the in vitro experiments are live microscopy experiments. 